Smooth Subdivision Surfaces Based on Triangles by Charles Loop (1987)

Official publication record: www.microsoft.com/en-us/research/publication/smooth-subdivision-surfaces-based-on-triangles/

Master's thesis, Department of Mathematics, University of Utah. The publication page confirms author, title and year; its large PDF was not accessible through the browser during this review. The original-mask formulas are instead checked against Loop's accessible 2000 report.