The problem is investigated from three different perspectives: (i)
Using kown positions and distances we derive the inclination of a
plane passing through the Milky Way and M31 and minimizing the
distances of all remaining objects to it.  This plane is indeed a
planar slab of about 300 kpc thickness.  (ii) The existence of this
plane is then tested by the Minimum Action method. The geometrical and
Minimum Action planes are coincident. Furthermore, passing from the
Minimum Action to the force field exerted by galaxies and galaxies
groups external to the local Group, the external force filed is found
to run parallel to this plane. (iii) Finally, we investigate whether
the planar distribution of dwarf galaxies (in particular of the most
distant ones) can be the results of tidal forces exerted by the
external galaxies/groups. We find that the geometrical structure
minimizing the energy of tidal interactions is a plane coincident in
orientation with the previous ones. The situation is remarkable stable
over long periods of time.

Stefano Pasetto & Cesare Chiosi