F. M. Wigley, L. W. Moreland, B. Zee, J. Varga, E. V. Lally, R. W. Martin, V. D. Steen, P. Brennan, B. White, P. J. Clements, Maureen D Mayes, P. A. Lachenbruch, M. Weisman, A. J. Silman, N. Allegar, F. Ingenito, M. Massa, D. McCloskey, J. R. Seibold,
Skin thickness score in systemic sclerosis: an assessment of interobserver variability in 3 independent studies. The Journal of Rheumatology. ,vol. 20, pp. 1892- 1896 ,(1993)