Plakhta, L. P. “Restrictions on Free Actions of the Alternating Group $A_6$ on Products of Spheres”. Ukrains’kyi Matematychnyi Zhurnal, vol. 48, no. 10, Oct. 1996, pp. 1431-4, https://umj.imath.kiev.ua/index.php/umj/article/view/5229.