1929-56-2 1H-Pyrazole-3-carboxylic acid, 4-((4-chloro-2-nitrophenyl)azo)-4,5-dihydro-5-oxo-1-phenyl-, ethyl ester 2-Pyrazoline-3-carboxylic acid, 4- (4-chloro-2-nitrophenyl)azo -5-oxo-1-phenyl-