1. K. Borsuk, Theory of Retracts. Monografie Matematyczne 44, PWN, Warsaw, 1967.
2. K. Borsuk, Theory of Shape. Lecture Notes Series 28, Matematisk Institut, Aarhaus Universitet, Aarhaus, 1971.
3. Clapp M. H.: On a generalization of absolute neighborhood retracts. Fund. Math. 70, 117–130 (1971)
4. R. Engelking, General Topology. PWN, Warsaw, 1977.
5. L. Górniewicz, Topological Fixed Point Theory of Multivalued Mappings. Springer, Dordrecht, The Netherlands, 2006.