Ling, Gao, et al. “Epidermal p53 Response and Repair of Thymine Dimers in Human Skin After a Single Dose of Ultraviolet Radiation: Effects of Photoprotection”. Acta Dermato-Venereologica, vol. 81, no. 2, Mar. 2001, pp. 81-86, doi:10.1080/00015550152384173.