1. Bochner S., Martin W. T., Functions of Several Complex Variables, Princeton, 1948.
2. 2. Vainberg M. M., Variational Methods In The Study Of Non-linear Operators, Gostekhizdat, 1956
3. 3. translation by Holden-Day, San Francisco, 1964.
4. Gel’man A. E., Implicit abstract function theorems, Dokl. Akad. Nauk SSSR 132 (1960) 501–503.
5. Gel’man A. E., On analytic solutions of essentially non-linear equations, Dokl. Akad. Nauk SSSR 144 (1962) 19–20.