W. Star, A. van’t Veen, D. Robinson, K. Munte, E. de Haas, and H. Sterenborg, “Topical 5-aminolevulinic acid mediated photodynamic therapy of superficial basal cell carcinoma using two light fractions with a two-hour interval: long-term follow-up”, Acta Derm Venereol, vol. 86, no. 5, pp. 412–417, Sep. 2006.