On the coverings of Euclidian manifolds ${\mathcal{B}}_1$ and ${\mathcal{B}}_2$

There are just 10 closed flat 3-manifolds, following [1], we call them platycosms. The aim of this paper is to classify types of n-coverings over amphicosms, i.e. some kinds of platycosms, and enumerate the numbers of them. Key words: platycosm, amphicosms, flat 3-manifold, non-equivalent covering over manifold, crystallographic group.