Muratbekov, M.B., and M.M. Muratbekov. “On the Bounded Invertibility of a Schrödinger Operator With a Negative Parameter in the Space L2(Rn )”. Bulletin of the Karaganda University. Mathematics Series 93, no. 1 (March 30, 2019): 36–47. Accessed September 5, 2025. http://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/258.