Human skin levels of retinoic acid and cytochrome P-450-derived 4-hydroxyretinoic acid after topical application of retinoic acid in vivo compared to concentrations required to stimulate retinoic acid receptor-mediated transcription in vitro - Duell, E A; Aström, A; Griffiths, C E; Chambon, P; Voorhees, J J (J Clin Invest, 1992)