GirikE. A. (1993) “On the existence of vector fields with a given set of singular points on a two-dimensional closed oriented manifold”, Ukrains’kyi Matematychnyi Zhurnal, 45(12), pp. 1706–1709. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/5980 (Accessed: 27July2024).