1. K. Gerlach, E. Kessler and W. Henne, Hollow fiber membrane for plasma separation, U.S. Pat. 4,708,799 (1987).
2. T. Ichikawa, K. Takahara, K. Shimoda, Y. Seita and M. Emi, Hollow fiber membrane and method for manufacture thereof, U.S. Pat. 4,708,800 (1987).
3. K. Kamada, S. Minami and K. Toshida, Porous polypropylene hollow filaments and the method making the same, U.S. Pat. 4,055,696 (1977).
4. M. Shino, T. Yamamoto, O. Fukunage and H. Yamamori, Process for making microporous polyethylene hollow fibers, U.S. Pat. 4,530,809 (1985).
5. M.L. Druin, J.T. Loft and S.G. Plovan, Novel opencelled microporous film, U.S. Pat. 3,801,404 (1974).