A. M. Baranovich and Y. L. Daletskii, “Differential-geometric relations for a class of formal operator power series”, MFAT, vol. 2, no. 1, pp. 1–16, Apr. 1996, Accessed: Dec. 19, 2025. [Online]. Available: https://zen.imath.kiev.ua/index.php/mfat/article/view/6