  A Dehn sphere in a closed 3-manifold M is a 2-sphere immersed in M with only
double curve and triple point singularities. The Dehn sphere S fills M if it
defines a cell-decomposition of M. The inverse image in S^{2} of the double
curves of S is the Johansson diagram of S and if S fills M it is possible to
reconstruct M from the diagram. A Johansson representation of M is the
Johansson diagram of a filling Dehn sphere of M. In a recent paper of J. M.
Montesinos it is proved that every closed 3-manifold has a Johansson
representation coming from a nulhomotopic filling Dehn sphere. In this paper a
set of moves for Johansson representations of 3-manifolds is given. In a
forthcoming paper it is proved that this set of moves suffices for relating
different Johansson representations of the same 3-manifold coming from
nulhomotopic filling Dehn spheres. The proof of this result is outlined here.
