U.S. Department of Energy
U.S. Department of Justice
U.S. Internal Revenue Service
UBS Investment Bank
Ultramar Oil and Gas Ltd.
Unexco Inc.
Union Petroleum Co.
Unit Corp.
United Energy Group Ltd.
United Natuional Group
Universal Resources Corp.
U.S. Department of Interior (MMS)
U.S. Energy Corp.
UB15 Petroecuador
Ultra Petroleum Corp.
UMC Petroleum Corp.
UniCorp Inc.
Unisource Energy Corp.
Unit Drilling and Exploration Co.
United Gas Holding Corp.
United Utilities Corp.
University of Texas System
Ural Petroleum Corp.