1. F. B. Downing, A. E. Parmalee and C. J. Pedersen: U.S. Patent 2,004,160 (6/11/35) to Du Pont.
2. F. B. Downing and C. J. Pedersen: U.S. Patent 2,008,753 (7/23/35) to Du Pont; also 2,087,103 (7/13/37).
3. R. G. Clarkson and C. J. Pedersen: U.S. Patent 2,054,282 (9/15/36) to Du Pont.
4. L. Spiegler and C. J. Pedersen: U.S. Patent 2,087,098 (7/13/37) to Du Pont.
5. F. B. Downing and C. J. Pedersen: U.S. Patent 2,121,397 (6/21/38) to Du Pont.