CΓ-PROPERTY AND APPROXIMATELY DIFFERENTIABLE FUNCTIONS Article Isakov N.M. Mathematical Notes. Vol. 44. 1988. P. 833-842
THEOREMS ON THE SMOOTHNESS OF THE RIGHT INVERSE Article Isakov N.M. Mathematical Notes. Vol. 41. 1987. P. 124-131
A GLOBAL PROPERTY OF APPROXIMATELY DIFFERENTIABLE FUNCTIONS Article Isakov N.M. Mathematical Notes. Vol. 41. 1987. P. 280-285