In Bullock v. Enserch Exploration, Inc., 614 S.W.2d 215 (Tex.Civ.App.--Austin 1981, writ ref'd n.r.e.), cert. denied, 455 U.S. 946 (1982), the "critical issue was whether Enserch's sale of natural gas with deliveries by pipeline in Texas to interstate companies for resale outside of Texas constituted "business done in Texas." Id. at 216. The court held that the sale of gas by a Texas gas company to an interstate pipeline company for resale outside of Texas represented "gross receipts from its business in Texas." 614 S.W.2d at 217.