Citation: Aw. Erian et al., POLYFUNCTIONALLY SUBSTITUTED HETEROCYCLES - SYNTHESIS OF NEW POLYFUNCTIONALLY SUBSTITUTED PHTHALAZINES, PYRIDO[3,4-C]PYRIDAZINES AND PYRAZOLO[3,4-C]PYRIDAZINES, Phosphorus, sulfur and silicon and the related elements, 122, 1997, pp. 133-141