TY JOUR TI Leadership styles and professional identity of managers at different stages of professionalization: differences and a mathematical model of differentiation KW psychology of professional activity KW leadership styles KW professional identity KW coping behavior models KW differentiation model KW managers JO Scientific notes of P. F. Lesgaft University AU Dmitrieva, Y.A. AU Borisova, O.V. AU Koltunov, E.I. PY 2026 IS 0 PB National State University of Physical Education, Sports and Health named after P.F. Lesgaft