Heickendorff, L, et al. “Serum Aminoterminal Propeptide of Type III Procollagen in Systemic Sclerosis. A Follow-up--Investigations in Subclasses and During Therapy”. Acta Dermato-Venereologica, vol. 71, no. 3, Jan. 1991, pp. 185-8, doi:10.2340/0001555571185188.