Yerkex, A.T., and T.N. Bekzhan. “On Outer Elements of the Noncommutative Hp Spaces”. Bulletin of the Karaganda University. Mathematics Series 77, no. 1 (March 28, 2015): 56–59. Accessed August 26, 2025. http://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/11.