Ultramar Diamond Shamrock Corporation History

Address:
6000 North Loop 1604 West
San Antonio, Texas 78249
U.S.A.

Telephone: (210) 592-2000
Fax: (210) 592-2054

Website:
Public Company
Incorporated: 1910 as Diamond Alkali Company
Employees: 24,000
Sales: $11.14 billion (1998)
Stock Exchanges: New York Montreal
Ticker Symbol: UDS ULR
NAIC: 32411 Petroleum Refineries; 48691 Pipeline Transportation of Refined Petroleum Products; 48621 Pipeline Transportation of Natural Gas; 454311 Heating Oil Dealers; 42271 Petroleum Bulk Stations and Terminals; 44711 Gasoline Stations with Convenience Store; 32511 Petrochemical Manufacturing

Company Perspectives:

Be the Best--Win and Grow. Focus on our customers; produce and provide quality products and services. Improve everything we do; create opportunities out of change; control costs; and outperform competition. Encourage each employee's participation and ideas; communicate openly and honestly; value, respect, and develop every employee. Be safe; ethical; responsible and protective of the environment; have fun; and take pride in our work. Key Dates:

Key Dates:

1910:
Diamond Alkali Company is formed to produce chemicals for the glass industry.
1936:
Company begins the production of magnesium oxide, used in the manufacture of incendiary bombs.
1967:
Diamond merges with Shamrock Oil and Gas Company to form Diamond Shamrock Corporation.
1983:
Diamond Shamrock merges with Natomas Company and gains oil and gas wells in Canada, Indonesia, and the North Sea.
1987:
Restructuring leads to the formation of Diamond Shamrock R & M, Inc., an independent oil refining and marketing company.
1989:
Company enters the petrochemicals industry.
1990:
Company's name is changed to Diamond Shamrock, Inc.
1996:
Diamond Shamrock Corporation and Ultramar Corporation merge to form Ultramar Diamond Shamrock Corporation.

Company History:

Ultramar Diamond Shamrock Corporation (UDS), based in San Antonio, Texas, is the second largest independent oil refining and marketing company in the United States. UDS, which was formed in late 1996 through the merger of Ultramar Corporation and Diamond Shamrock, Inc., owns seven refineries, located in California, Texas, Oklahoma, Colorado, Michigan, and Quebec, Canada. The refineries have a combined capacity of 685,000 barrels per day. The company also owns some 6,000 retail gasoline and convenience store outlets in the United States and Canada. The majority of the gasoline stations are branded Diamond Shamrock, Ultramar, Beacon, or Total. UDS also operates petrochemical and home heating oil businesses.

Beginnings Rooted in Glassmaking: 1910--45

In 1910 a group of Pittsburgh businessmen associated with the glass industry formed the Diamond Alkali Company to produce soda ash, a basic raw material of glass manufacturing. Diamond Alkali was incorporated in West Virginia in March of that year, with the company's headquarters established in Pittsburgh. The new corporation was capitalized at $1.2 million, with most of the funds going toward the construction of a soda ash plant in Painesville, Ohio.

After World War I began, the demand for canning glass increased, and Diamond Alkali found a niche in the market. At about the same time Diamond Alkali began marketing increasing quantities of its soda ash for laundry preparations, baking soda, water softeners, paper and pulp production solutions, and textile processing. By 1915 Diamond's ability to produce soda ash exceeded customer demand, and the company began using soda ash and limestone to produce caustic soda. This development opened new markets in lye, soap, detergents, and, eventually, rayon and cellophane. In 1918 Diamond began making bicarbonate of soda. A short time later the company's product line was expanded beyond the basic alkalis of soda ash, caustic soda, and bichromates. In 1920 Diamond opened a second plant in Cincinnati to produce silicate of soda by combining soda ash with sand.

The company expanded its product line again in 1925 when the Painesville plant began to manufacture calcium carbonates, cement, and coke. A sludge by-product of soda ash was treated to make the calcium carbonate, marketed as an agent to give paint smoothness, speed dry printers' inks, and add physical properties to rubber and plastic products. In 1929 the company began making caustic soda through the new process of electrolysis of salt, a method of running brine through electricity. Two by-products formed from the process, chlorine and pure hydrogen, also were marketed. Chlorine was sold to the water purification industry and also was used in the manufacture of dry cleaning solvents. The hydrogen was used for hydrochloric acid production, welding fuel, food oil hardening, electric lamp production, and ammonia production.

Diamond began a modest research program in 1936 that resulted in the production of magnesium oxide. After World War II began, magnesium became an important component for incendiary bombs, and Diamond was selected by the United States to operate one of 12 government-owned magnesium plants. Diamond's first research laboratory was established in 1942 by Raymond F. Evans, son of Diamond founder T.R. Evans. He became general manager of the company the following year.

By 1944 Diamond was operating three plants constructed through Defense Plant Corporation funds, including the magnesium plant, a calcium hypochlorite plant, and a synthetic catalyst plant under joint lease with the M.W. Kellogg Company. Before the war concluded, Diamond acquired Emeryville Chemical Company, a West Coast manufacturer of silicate of soda.

Rapid Diversification Following World War II

After 1945 Diamond's focus turned to a program of selling unprofitable assets, simplifying corporate structure, and modernizing, expanding, and adding plants. During the late 1940s several new plants opened, including a chlorine and caustic soda plant, a magnesium oxide plant, a silicate plant, and an electrochemical plant. Diamond signed five-year lease agreements with the U.S. government for chlorine and caustic soda plants at the U.S. Army chemical corps arsenal at Edgewood, Maryland, and at Pine Bluff, Arkansas. Detergent plants were established in Dallas and Painesville and at Emeryville, California.

Around 1947 the government lifted price controls imposed during the war, and Evans, appointed company president in 1947, directed Diamond's first price hike in nine years, seeking to reverse a wartime downward trend in earnings. A year later Diamond moved its headquarters from Pittsburgh to Cleveland, closer to its central operations in Painesville. Sales passed the $50 million mark for the first time in that year, but they slumped in 1949 due in part to a two-month strike that cost the company about $750,000 in net earnings. Diamond boosted its bichromate production with the acquisition of the Martin Dennis Company, operator of two New Jersey plants. With export sales on the rise, in 1949 Diamond formed an exports sales division that included Martin Dennis.

By 1950 Diamond's first phase of postwar expansion and diversification was nearly complete, with the company's assets having grown to include 12 different plants producing more than 100 different chemicals. In mid-1950, after the United States entered the Korean War, the demand for Diamond's products increased. The war also spurred the U.S. government to reactivate the Painesville magnesium plant that Diamond had operated during World War II, and the company was again charged with operating the facility, forfeiting any profit.

During the first half of the 1950s, Diamond embarked on its second phase of postwar growth by implementing diversification, geographical expansion, and modernization programs that helped it gain entry into the organic and agricultural chemicals, plastics, and chromic acid fields. In the fall of 1950 Diamond acquired the chromic acid business of E.I. du Pont de Nemours and Company. One year later Diamond purchased Kolker Chemical Works, Inc., a manufacturer and distributor of organic insecticides and agricultural chemicals, including DDT. In 1953 Diamond Alkali began producing polyvinyl chloride, a product used in the manufacture of plastic articles, and perchloroethylene, a product used in metal cleaning and dry cleaning. That same year Diamond acquired Belle Alkali Company, a producer of chemicals used in the manufacture of silicone resins, solvents, and drugs.

Evans became company chairman in 1954, and John A. Sargent, executive vice-president, became president. In the same year Diamond created an exploratory research department to assist in strategic planning. Diamond continued its geographical diversification in early 1955 with the acquisition of a 51 percent interest in Diamond Black Leaf Company, an agricultural chemicals firm with plants in Virginia, Alabama, Kentucky, and Texas. Two years later Diamond Black Leaf became a wholly owned subsidiary.

In 1955 Diamond acquired a government-owned chlorine and caustic soda plant at Muscle Shoals, Alabama, for $15 million. That same year the company passed the $100 million sales mark for the first time, logging $110 million in revenue. While sales were increasing, Diamond's name recognition outside the chemical industry lagged, and in 1956 Diamond joined a number of chemical companies adopting new trademarks. The former 'alkali' enclosed in a horizontal diamond was replaced by a vertical diamond surrounded by a curved letter 'd.' In 1957 Sargent resigned, and Evans assumed the additional duties of president.

Diamond's growth continued in the 1960s. In 1960 Bessemer Limestone & Cement Company, an operator of a cement plant and limestone quarries, was merged into Diamond. Diamond also acquired Harte & Company, a producer of vinyl film and sheeting that served the plastics industry, and Chemical Process Company, a producer of chemicals used for water purification, pharmaceuticals, and polyester resins. In 1961 Diamond joined three foreign firms in building a $15 million electrolytic caustic chlorine plant in Brazil, the largest in South America, to produce fertilizer chemicals. The following year Diamond and a French firm, Prosim, S.A., formed the joint venture company Dia Prosim, S.A., to manufacture water treatment chemicals at a new plant in Mobile, Alabama.

Arthur B. Tillman, who had worked his way through the ranks from division manager to company vice-president, was named president in 1966. In 1967 Diamond merged with Nopco Chemical Company, a New Jersey producer of a wide range of inorganic and organic chemicals. Also that year, Diamond acquired the polypropylene resin and film plants of Alamo Industries, boosting its foothold in the plastics market.

Expansion into the Oil Industry and Continued Diversification: Late 1960s--70s

In the summer of 1967 Diamond laid the foundation for expansion into the petrochemicals field by merging with Shamrock Oil and Gas Company to form Diamond Shamrock Corporation (Diamond). The merger combined Diamond Alkali's chemical assets with Shamrock Oil's production interests in oil, gas, and petrochemical fertilizers and its marketing assets, which included a chain of service stations.

Evans was named chairman of the new corporation, and James A. Hughes, a former Diamond Alkali vice-chairman, became president. C.A. Cash, former Shamrock president, became executive vice-president and president of the new subsidiary Diamond Shamrock Oil and Gas Company, while Tillman also was named executive vice-president of the corporation and president of the new subsidiary Diamond Shamrock Chemical Company. J.H. Dunn, former Shamrock chairman, was named chairman of the executive committee of the board.

In 1968 Diamond Shamrock sold its Bessemer Cement division to Louisville Cement Co. for $20 million to comply with a Federal Trade Commission ruling to divest itself of the unit. One-quarter of Diamond Shamrock's sales that year came from oil and gas, with the remainder of its revenues coming from a mix of commodity chemicals, plastics, specialty chemicals, and agricultural chemicals. The mix changed in 1969 after Diamond acquired Taylor-Evans Seed Company, a producer of farming seeds with international marketing operations, and Pickland Mather & Company, a leading supplier of raw materials to the steel industry, with interests in iron ore mining, mineral management, and ocean shipping vessels.

Diamond's oil exploration activities during the early 1970s focused in large part on the Gulf of Mexico, Gulf of Alaska, North Sea, and Texas Panhandle, while production centered on domestic drilling in the West and Southwest. In 1971 Diamond Shamrock's growing interest in the fields of animal health and veterinary medicine led to the purchase of BioToxicological Research Laboratories, which was engaged in chemical research related to agriculture and animal health. The following year Diamond acquired American Chocolate & Citrus Company of St. Louis, a provider of flavorings, fruit drink bases, and food processes to commercial dairies. Three years later Hughes retired, and Cash was named chairman. William H. Bricker, who had joined the company in 1969 as a vice-president overseeing agricultural chemicals, was named president. In 1976 he was named chief executive officer.

Diamond's specialty chemical operations continued to grow during the late 1970s. The company expanded its foothold in the commercial baking market when it bought three Philadelphia-based providers of baking supplies: Federal Yeast Corporation, Gold Star Foods Company, and Bakery Products Inc. Diamond also acquired the animal health business of Shell Chemical Company and expanded its existing vinyl chloride and potassium carbonate plants.

Diamond continued to build on a growing oil and gas foundation, with the area of exploration more than doubling between 1972 and 1977 to more than 2.5 million acres, while oil production increased more than 60 percent. In 1977 Diamond announced plans to construct a $25 million catalytic cracking unit at its McKee refinery near Dumas, Texas, to meet federal regulations calling for increased production of unleaded gasoline. The following year Diamond acquired a 21 percent stake in Sigmor Corporation of San Antonio for $28 million and then sold Sigmor $19 million in service station properties, a majority of which carried the Shamrock brand.

After Cash retired in 1979, Bricker assumed the additional duties of chairman and moved to make Diamond a major energy company. That same year Diamond acquired Falcon Seaboard Inc., a Houston-based producer of steam coal for $250 million. In a move that prompted Evans to resign as a director, Bricker relocated the company's headquarters from Cleveland to Dallas to follow its growing energy interests in the Southwest. Reflecting the change in Diamond Shamrock's focus, the 1979 annual report noted that the 'energy, technology and chemicals' company had more than quadrupled during the decade.

Consolidation and Increasing Challenges in the Early 1980s

Diamond Shamrock entered the 1980s with a new president, Allan J. Tomlinson, a former executive vice-president in charge of the company's international and technology unit. In 1980 Diamond announced a slate of divisions targeted for divestiture, including plastics, metal coatings, domestic polymers, food-related products, animal nutrition, and medical products.

While courting buyers for its chemical assets, in 1980 Diamond turned its acquisition goals toward coal. The company paid $30 million for undeveloped coal reserves and then formed a coal marketing subsidiary. In 1981, in a second major expansion move into coal, Diamond purchased Amherst Coal Company for $220 million and then reached an agreement with the French government to provide steam coal for power generation. Diamond posted record earnings in 1981 of $230 million on $3.4 billion in sales.

In 1982, after having spent $161 million for drilling rights in Alaska's Beaufort Sea, earnings dropped by roughly $150 million because of recessionary conditions and falling energy prices. J.L. Jackson, former president of Diamond's coal unit, was named corporation president in 1983. Diamond continued seeking buyers for its weak chemical assets, and the company expanded its divestiture slate to include its water conditioning and process chemical divisions. Diamond permanently laid off 500 workers in 1983 but still reported a $60 million loss due to tax write-offs on a dry hole in the Beaufort Sea. Diamond's most expensive move of 1983 was its $1.2 billion stock swap in the merger with Natomas Company. The merger gave Diamond oil and gas operations in Indonesia, a geothermal energy business, and wells producing oil in the North Sea, Canada, and the United States.

Diamond's involvement with the defoliant Agent Orange in the mid-1960s affected the company in 1984. In March 1984 Diamond agreed to spend $412 million to clean up contaminants at a New Jersey plant where it had produced the defoliant for use during the Vietnam War. Two months later Diamond was one of seven chemical companies that agreed to a settlement to compensate Vietnam War veterans for injuries claimed to be associated with exposure to dioxin, a toxic substance used in Agent Orange. Although Diamond Shamrock produced only five percent of the Agent Orange used in the Vietnam War, the company's chemical compound contained the highest concentration of dioxin. In the settlement Diamond agreed to contribute $21.6 million to a compensation fund.

Turbulent Times in the Late 1980s

In 1985 Bricker tentatively agreed to sell Diamond for $28 a share to Occidental Petroleum Corporation but then withdrew the offer. The scrapped deal drew takeover speculation, and Diamond announced a restructuring to fend off possible hostile maneuvers. Included in the restructuring was the formation of a master limited partnership, Diamond Shamrock Offshore Partners Ltd., to hold the company's oil and gas assets in the Gulf of Mexico. Diamond also announced $810 million in write-offs, in large part due to its Indonesian properties, and said that it would repurchase about six percent of its stock.

In 1986 the company announced that it would eliminate 600 more jobs, sell its chemical and coal operations, and increase its oil and natural gas reserves. Jackson resigned a few months after the announcement. Later that year, Diamond's chemical business was sold to Occidental Petroleum for $850 million. With Diamond retrenching, in December 1986 Texas oilman T. Boone Pickens, who controlled the oil firm Mesa Limited Partnership, offered $2 billion for Diamond in a securities exchange. The offer was dropped a few weeks later, after Diamond had rejected the bid and filed suit against Pickens.

A second bid from Pickens in early 1987 prompted Diamond to announce its third restructuring in two years. Bricker, in his last move as chairman, had the company split in two to form a production and exploration company, named Maxus Energy Corporation, and an independent refining and marketing company, which kept the Diamond Shamrock name and became Diamond Shamrock R & M, Inc., to be based in San Antonio. Roger R. Hemminghaus, who had been running Diamond's refining business for two years, was named president. Assets for the new company included $1.6 billion in sales; two Texas refineries in McKee and Three Rivers; a natural gas processing plant; 4,000 miles of pipeline; 2,000 branded stations in 12 states; 550 company-operated retail stores in Texas, Colorado, and Louisiana; a lube oil blending and automotive accessories distribution company; and a liquid propane gas underground storage facility in Mont Belvieu, Texas, with a capacity of 30 million barrels. The new Diamond Shamrock went public in 1987.

Hemminghaus announced that Diamond Shamrock R & M would sell its more remote assets and concentrate on marketing operations in the Southwest. In 1988 the company began expanding its refinery and pipeline capacity and bolstering its retail presence. In the same year construction began on a $25 million hydrocracker unit for its McKee refinery, and Diamond purchased 80 Texas gasoline stations. In 1989 the company also established a development and new ventures department to identify related businesses in fields where it had expertise. Profits soared from $1.6 million in 1987 to $53.5 million in 1988, while stock prices nearly doubled to $28. Diamond formed the subsidiary, Diamond Shamrock Natural Gas Marketing Company, and then purchased two companies, Merit Tank Testing, Inc., which provided environmental testing for underground petroleum storage, and Petro/Chem Environmental Services, Inc., which marketed petroleum-related environmental services. The two were merged under the Petro/Chem name in 1989.

In 1989 Diamond entered the petrochemicals business and became a 33 percent partner in a propane-propylene operation in Mont Belvieu. Diamond's Mont Belvieu underground storage facility became the world's largest that year with the acquisition of XRAL Storage and Terminaling Company, which raised the company's capacity to 50 million barrels. Diamond also acquired a telephone services company and formed the subsidiary North American InTeleCom, Inc., a firm that was based in San Antonio and that provided operator-assisted services for correctional facilities and that managed private pay telephones, including those at many of Diamond's retail outlets.

Continued Changes and Challenges in the 1990s

In 1990 the company name was changed to Diamond Shamrock, Inc., and the company completed projects to pave the way for growth in the new decade, including major refinery additions, pipeline expansions, and the addition of some 40 new retail outlets. To increase its presence in the retail gasoline market in the Southwest, Diamond purchased 661 National Convenience Stores in Texas for $260 million in 1995. Also in 1995 Argentine oil company YPF purchased Maxus, Diamond's exploration and production business.

A major change occurred in December 1996 when Diamond merged with Ultramar Corporation to form Ultramar Diamond Shamrock Corporation (UDS). Ultramar had been founded in 1935 as Ultramar Exploration Co. Ltd., a company focused on developing oil fields in Venezuela. Beginning in the 1950s the company's operations spread into Canada, the United States, and Europe, and by 1975 Ultramar's assets included more than 1,000 retail gas stations in eastern Canada. The state of the oil industry in the 1980s created problems for Ultramar, however, and in 1991 the British oil firm LASMO purchased Ultramar in a hostile takeover. The following year LASMO spun off Ultramar's refining and marketing operations in North America as Ultramar Corporation.

The newly formed Ultramar Diamond Shamrock bought Total Petroleum (North America) Ltd. in September 1997, adding three refineries, in Oklahoma, Michigan, and Colorado, and some 2,000 gas stations in the central United States to Ultramar's operations. The merger and the acquisition resulted in increased net income for the company in 1997. Net income was $154.8 million, up significantly from 1996, but it amounted to a loss of $35.9 million.

In June 1998, with the hope of improving profitability and operating efficiencies, the company adopted a major restructuring plan. The plan included the sale or closure of more than 300 convenience stores, the cutting of more than 450 jobs, and the reorganization of some pipeline and refinery operations. The company planned to record a one-time pretax charge of $130 million for the quarter ended June 30, 1998, because of the restructuring. UDS president and COO Jean Gaulin voiced his support of the plan in a prepared statement and said, 'The restructuring will reduce costs and increase our customer focus. . . . The initiatives we are announcing today [June 9, 1998] will dramatically improve our operating performance and help us achieve our objectives for market leadership and higher return on capital employed.' In the second half of 1998 UDS began to carry out its plan, selling or closing 65 convenience stores and eliminating nearly 200 employee positions. At the beginning of 1999 UDS announced plans to cut all nonessential and underperforming jobs and programs, which resulted in the almost immediate termination of 300 employees, including six vice-presidents. The layoffs raised the total job cuts to more than 1,300 since the merger that had created UDS in 1996.

UDS's improvement strategy included seeking beneficial joint ventures, and in July 1998 the company announced that it had reached a definitive agreement with utilities provider PG & E Corporation to manage UDS's energy services. The $2 billion, seven-year energy alliance was intended to assist UDS in reducing its energy costs. In September UDS formed Diamond-Koch L.L.C. with Koch Hydrocarbon Company, Koch Pipeline Company, L.P., and Koch Chemical Company, a division and subsidiaries of Koch Industries, Inc., respectively. The joint venture added several pipeline segments and a natural gas liquids fractionator to UDS's petrochemical assets.

Several attempts by UDS to streamline its operations in the wake of declining crude oil prices were foiled. In early 1998 the company signed an agreement with Petro-Canada to form a joint venture in which UDS's Canadian and northern U.S. operations would be combined with Petro-Canada's. When the Competition Bureau of Canada raised concerns regarding the venture, UDS terminated the project in June 1998. In October UDS entered into discussions with Phillips Petroleum Co. about the tentative formation of a refining and marketing joint venture. The North American venture was to include the operating assets of UDS and the North American refining, marketing, and transportation operations of Phillips. Unable to reach agreeable terms, however, the deal was terminated in March 1999. In another setback, UDS announced plans to close its refinery in Alma, Michigan, in October 1999. The refinery had been offered for sale, but no buyer materialized. UDS did, however, locate a buyer for its retail stores, terminals, and pipelines located in Michigan when it agreed to sell the operations to Marathon Ashland Petroleum L.L.C.

Despite the setbacks presented by the low refinery margins in the oil business and the failed mergers and ventures, UDS believed that its restructuring strategy would help modernize the company, eventually leading to increased productivity and success. The company experienced an upward trend as it headed toward the new millennium; in the second quarter of 1999, ended June 30, net income reached $48.4 million, a marked improvement over the same period in 1998, when UDS had reported a net loss of $52.6 million. CEO Gaulin, who replaced Hemminghaus at the beginning of 1999 when the latter retired, announced at the 1999 company shareholders' meeting, 'Looking forward, we are focused on three objectives; continue to grow earnings per share, improve our competitive position, and further strengthen our balance sheet. . . . In summary, it is imperative that we have a clear goal--and we have it. We must successfully execute the goal--we have, and we are.'

Principal Subsidiaries: Autotronic Systems, Inc.; Diamond-Koch L.L.C. (50%); D.S.E. Pipeline Company; Diamond Shamrock Pipeline Company; Diamond Shamrock Refining Company, L.P.; Diamond Shamrock Refining and Marketing Company; Emerald Corporation; Emerald Pipe Line Corporation; Kempco Petroleum Company; National Convenience Stores Incorporated; Sigmor Corporation; Sigmore Pipeline Company; The Shamrock Pipe Line Corporation; Ultramar Ltd.; West Emerald Pipe Line Corporation.

Principal Competitors: BP Amoco Corp.; Exxon Corp.; 7-11, Inc.

Further Reading:

  • Atterbury, Paul, and Julia MacKenzie, A Golden Adventure: The First 50 Years of Ultramar, London: Hartwood Press, 1985.
  • Bricker, William H., Partners by Choice and Fortune: The Story of Diamond Shamrock, Princeton, N.J.: Princeton University Press, 1977.
  • Johnston, David, 'Phillips, UDS Call Off U.S. Downstream JV,' Platt's Oilgram News, March 23, 1999, p. 1.
  • Lee, Steve H., 'Ultramar To Acquire Total Petroleum,' Dallas Morning News, April 16, 1997, p. D2.
  • Mason, Todd, and G. David Wallace, 'The Downfall of a CEO: The Inside Story of Bill Bricker's Reign at Diamond Shamrock,' Business Week, February 16, 1987.
  • Norman, James, 'Phillips, UDS Join in U.S. Refining Venture,' Platt's Oilgram News, October 9, 1998, p. 1.
  • 'Petro-Canada, UDS Form Joint Venture,' National Petroleum News, February 1, 1998, p. 22.
  • Spencer, Starr, 'UDS Sells Michigan Retail, To Shut Refinery,' Platt's Oilgram News, May 25, 1999, p. 1.
  • 'Ultramar Diamond Shamrock Hires PG & E To Manage All Its Power and Gas Supplies,' Industrial Energy Bulletin, March 20, 1998, p. 1.
  • 'Ultramar, Diamond Shamrock Merge `Unique,' National Petroleum News, November 1, 1996, p. 19.
  • 'Ultramar Diamond Shamrock Restructures Operations,' National Petroleum News, July 1, 1998, p. 13.
  • Zipf, Peter, 'Ultramar Diamond's Plan Targets Lagging Returns,' Platt's Oilgram News, November 19, 1997, p. 1.

Source: International Directory of Company Histories, Vol. 31. St. James Press, 2000.