5-Oxo-1-(4-sulfophenyl)-4-[(4-sulfophenyl)azo]-2-pyrazoline-3-carboxylic acid

4-(4-Sulfophenylazo)-1-(4-sulfophenyl)-4,5-dihydro-5-oxo-1H-pyrazole-3-carboxylic acid

4,5-dihydro-5-oxo-1-(4-sulphophenyl)-4-[(4-sulphophenyl)azo]-1H-pyrazole-3-carboxylic acid