ABSTRACT
D on S. By definition, every embedding of D on S is induced by an embedding of ID as described. For each B ∈ B the open topological disc bounded by the closed walk e1e2 . . . ek in H(ID) and having contained B before discarding is a block region; the remaining regions are nonblock regions. The embedding of D is cellular if each nonblock region (and hence each region) of the embedding is homeomorphic to an open disc.
