Humbert, P, et al. “Treatment of Scleroderma With Oral 1,25 Dihydroxyvitamin D3: Evaluation of Skin Involvement Using Non Invasive Techniques. Results of an Open Prospective Trial”. Acta Dermato-Venereologica, vol. 73, no. 6, Dec. 1993, pp. 449-51, doi:10.2340/0001555573449451.