M. Ekelund, R. Carstam, C. Hansson, H. Rorsman, and E. Rosengren, “Urinary excretion of 5-S-cysteinyldopa and 6-hydroxy-5-methoxyindole-2-carboxylic acid: differences between pigmented and albino mice”, Acta Derm Venereol, vol. 65, no. 5, pp. 437–439, Sep. 1985.