LETTER TO THE EDITOR

In volume 187, no. 5, p. 974, 1969, of Doklady Akademii nauk SSSR, our note was published (Yu. G. Borisovich, B. D. Gel’man, E. Mukhamadiev, V. V. Obukhovskii) devoted to the concept of the rotation of multivalued vector fields with convex images in linear spaces.

Only very recently the authors of the article became aware of the results of the Polish mathematicians A. Granas and J. W. Jaworowski (Bull. Acad. Polon. Sci., Série des Sci. math., astr. et phys.; 7 (1959), 191—194, 271—275, 277—283), devoted to the same question. For mappings with convex images, A. Granas constructed the concept of a characteristic equivalent to our concept of rotation and proved the fundamental theorems. The method differs from ours, which is based on elementary constructions. A. Granas and J. W. Jaworowski generalized individual theorems to mappings with acyclic images.

We take this opportunity to inform readers about these works.

Yu. G. Borisovich. E. M. Mukhamadiev