"Diamond Shamrock Corp. or Diamond Shamrock Refining and Marketing was an oil refinery and gas station company in the United States, headquartered in San Antonio, Texas.
Since 2001, it operates as a brand of Valero and has withdrawn the brand from a majority of Texas gas stations and had converted most of the stores to Valero or sold them off to Texaco or other companies." - (en.wikipedia.org 29.01.2020)
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