1. C.D. Coxe, US patient 2,585,444 (1948, Du Pont).
2. H. Porosoff, US patient 4,163,770 (1979, American Cyanamid).
3. C.C. Young and F. De Maria, US patient 4,283,365 (1961, American Cyanamid).
4. C.C. Young and F. De Maria, US patient 4,379,113 (1983, American Cyanamid).
5. F. De Maria and C.C. Young, US patient 4,303,607 (1981, American Cyanamid).