Vu Kim Tuan and S. B. . Yakubovich, “One criterion of unitarity of bilateral integral transformation”, Ukr. Mat. Zhurn., vol. 44, no. 5, pp. 697–699, May 1992, Accessed: Apr. 07, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/7967