Polar rings and the 3D-shape of dark matter
  Polar ring galaxies (PRG) are unique to give insight on the 3D-shape of dark
matter haloes. Some caveats have prevented to draw clear conclusions in
previous works. Also the formation mechanisms need to be well known. All
available information on the topic is reviewed, and criteria are defined for an
ideal PRG system, in the hope of removing the ambiguities and make progress in
the domain.
