Carcinogenic N-nitrosodimethylamine as a contamination in drugs containing 4-dimethylamino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one (amidopyrine, aminophenazone)Kann, Jüri; Eisenbrand, G.; Spiegelhalder, B.Arzneimittel-Forschung = Drug research1979