1. National Aniline & Chem. Co., U.S. Patent 2,211,943 (1940).
2. Eastman Kodak Co., U.S. Patent 2,659,739 (1953).
3. Eastman Kodak Co., U.S. Patent 3,279,880 (1966).
4. Interchemical Corp., U.S. Patent 3,189,398 (1965).
5. BASF, U.S. Patent 3,299,103 (1967).