R. G. Safaryan, “The McKean martingale for the homogeneous $R-D$-systems”, Ukr. Mat. Zhurn., vol. 45, no. 9, pp. 1315–1319, Sep. 1993, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5936