Plakhta, L. P. “Invariants of Knots, Surfaces in R 3, and Foliations”. Ukrains’kyi Matematychnyi Zhurnal 59, no. 9 (September 25, 2007): 1239–1252. Accessed February 17, 2026. https://umj.imath.kiev.ua/index.php/umj/article/view/3384.