1. J.M.S. Henis and M.K. Tripodi, Multicomponent membranes for gas separations, US Pat. 4,230,463 (1980).
2. I. Pinnau and J. Wind, Process for increasing the selectivity of asymmetric membranes, US Pat. 5,007,944 (1991).
3. R.A. Hayes, Surfactant treatment of polyaramide gas separation membranes, US Pat. 5,032,149 (1991).
4. R.A. Hayes, Surfactant treatment of aromatic polyimide gas separation membrances, US Pat. 5,034,024 (1991).
5. Composite hollow fiber membranes for gas separation: the resistance model approach;Henis;J. Membrane Sci.,1981