Idzik, A., W. Kulpa, and P. Maćkowiak. “Equivalent Forms of the Brouwer Fixed Point Theorem”. Topological Methods in Nonlinear Analysis, vol. 44, no. 1, Apr. 2016, pp. 263-76, https://apcz.umk.pl/TMNA/article/view/TMNA.2014.047.