V. S. Mazorchuk, “On unitarizable modules over generalized Virasoro algebras”, Ukr. Mat. Zhurn., vol. 50, no. 9, pp. 1278–1280, Sep. 1998, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4845