Lattimer, C. R., E. Kalodiki, M. Azzam, and G. Geroulakos. “An International Survey on the Interpretation of Pigmentation Using the C Class of the Clinical, Etiological, Anatomical, Pathophysiological Classification”. Veins and Lymphatics, vol. 2, no. 1, Aug. 2013, p. e15, doi:10.4081/vl.2013.e15.