WÓJCIK, Paweł. A simple proof of the Polar Decomposition Theorem. Annales Mathematicae Silesianae, [S. l.], v. 31, p. 165–171, 2016. Disponível em: https://journals.us.edu.pl/index.php/AMSIL/article/view/13948. Acesso em: 5 dec. 2025.