“…This problem, whose complexity status is currently unknown, was introduced in the late sixties by Barnett and Kynch [22] and then extensively studied by many researchers, who proposed both exact methods (see, e.g., Dowsland [109], AlvarezValdes et al [5], or Ahn et al [2]) and powerful heuristics (see, e.g., Lins et al [190] or Birgin et al [41]). The number of references being huge, we refer the interested reader to the recent, very complete survey by Silva et al [260].…”