1. b T. S.Gore, B. S.Jashi, S. V.Sunthankar and D. B.Tilak, Ed., “Chemistry of Natural and Synthetic Colouring Matters”, Academic Press, New York, N.Y, 1962, pp 573-587 and 615-643;
2. Heterocycles as Structural Units in New Optical Brighteners
3. a For the various examples related to the benzothiazole derivatives prepared see H. Iwato, N. Nichimura and J. Nakano, Japanese Patent 71 31 862 (1971);
4. Chem. Abstr., 75, 140831v (1971);