„Petroleum Club of Houston“. Greater Houston Convention and Visitors Bureau (2011). 2015-yil 2-aprelda asl nusxadan arxivlangan. Qaraldi: 2013-yil 10-may.
„Petroleum Club of Houston“. Greater Houston Convention and Visitors Bureau (2011). 2015-yil 2-aprelda asl nusxadan arxivlangan. Qaraldi: 2013-yil 10-may.