1. Second homology groups under light open maps;Baildon,1970
2. Open finite-to-one maps of contractible polyhedra onto a sphere;Bredon;Proc. Amer. Math. Soc.,1970
3. Finite-to-one open mapping on manifolds;Cernavskii;Trans. Math. Sk.,1964
4. Finite-to-one open mappings on manifolds;Cernavskii;Amer. Math. Soc. Transl.,1971
5. Differentiable open maps on manifolds;Church;Trans. Amer. Math. Soc.,1963