Reynalda, Bagas, Sisilia Sylviani, and Anita Triska. “Foundations of Krein Spaces and the Nonequivalence of Pythagorean Orthogonality”. Indonesian Journal of Applied Mathematics and Statistics 3, no. 1 (June 1, 2026): 27–32. Accessed November 3, 2026. https://idjams.com/index.php/jms/article/view/35.