British Association of Dermatologists and British Photodermatology Group guidelines for the safe and effective use of psoralen–ultraviolet A therapy 2015. (21st January 2016) - Ling, T.C.; Clayton, T.H.; Crawley, J.; Exton, L.S.; Goulden, V.; Ibbotson, S.; McKenna, K.; Mohd Mustapa, M.F.; Rhodes, L.E.; Sarkany, R.; Dawe, R.S.