Local knotting of submanifolds

In this paper the author investigates the modification of the fundamental group of the complement of a submanifold of codimension 2 by knotting in a neighborhood of one of its points. With the aid of such knotting he constructs closed nonorientable surfaces in $\mathbf R^4$ with finite noncommutative groups. In the appendix he constructs a nontrivial knot such that, knotting by means of it does not change the type of the simplest imbedding $\mathbf RP^2\to\mathbf R^4$.
Figures: 6.
Bibliography: 10 titles.