1. R.J. Plunkett, U.S. 2,230,654 (1941) to Du Pont.
2. W.E. Mochel et al, Ind. Eng. Chem. 40, 2285 (1948).
3. T.A. Ford, U.S. 2,458,054 (1949) to Du Pont.
4. W.E. Hanford and J.R. Roland, U.S. 2,468,664 (1949) to Du Pont.
5. H.E. Schroeder, U.S. 2,484,664 (1949) to Du Pont.