Plakhta, L. P. (2007). Invariants of knots, surfaces in <b>R</b> <sub>3</sub&gt;, and foliations. Ukrains’kyi Matematychnyi Zhurnal, 59(9), 1239–1252. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/3384