1. J. C. Becker, A. Casson, and D. H. Gottlieb, The Lefschetz number and fiber preserving maps, Bull. Amer. Math. Soc. 81 (1975), 425–427.
2. V. G. Boltjanskitikya, S. S. Ryškov, and Ju. A. Šaškin, On k-regular imbeddings and their application to the theory of approximation of functions, Uspehi Mat. Nauk 15 (1960), no. 6 (96), 125–132 (Russian); Amer. Math. Soc. Transl. (2) 28 (1963), 211–219.
3. K. Borsuk, On the k-independent subsets of the Euclidean space and of the Hilbert space, Bull. Acad. Polon. Sci. Cl. III. 5 (1957), 351–356.
4. F. R. Cohen, The homology of ln+1-spaces, n ⩾ 0, Lecture Notes in Mathematics, No. 533 (Springer-Verlag 1976), 207–351.
5. F. R. Cohen and D. Handel, k-regular embeddings of the plane, (submitted).