Y. M. Berezansky and M. I. . Gekhtman, “Inverse problem of spectral analysis and the non-Abelian chains of nonlinear equations ”, Ukr. Mat. Zhurn., vol. 42, no. 6, pp. 730–747, Jun. 1990, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/8829