Optimum porphyrin accumulation in epithelial skin tumours and psoriatic lesions after topical application of ς-aminolevulinic acid. - Fritsch,C.; Lehmann,P.; Stahl,W.; Schulte,K.W.; Blohm,E.; Lang,K.; Sies,H.; Ruzicka,T. (Br J Cancer, 1999)