1. Lyne, F. A. and Moss, G. E., Chem. & Ind., 1971, 388–392.
2. Schoch, T. J. and Maywald, E. C.,Analyt. Chem., 1956, 28(3), 382–387.
3. Berliner, E., Mühlenlab., 1939, 9, 13 and 87.
4. Gurr, E., The Rational Use of Dyes in Biology, Leonard Hill, London, 1965.
5. Armitage, F. D., Industrial Chemist, 1943, 18, 583.