Hussein , Ahmed Talip, Habeeb Kareem Abdulla, and Haider Jebur Ali. “Bourbaki and Palais Proper Actions on D-Algebra”. Earthline Journal of Mathematical Sciences 2, no. 1 (July 4, 2019): 265-282. Accessed December 2, 2021. https://earthlinepublishers.com/index.php/ejms/article/view/112.