A possible global group structure for exotic states
  Based on the fact that the long expected pentaquark which possesses the exotic quantum numbers of $B=1$ and $S=1$ was not experimentally found, although exotic states of $XYZ$ have been observed recently, we conjecture that the heavy flavors may play an important role in stabilizing the hadronic structures beyond the traditional $q\bar q$ and $qqq$ composites. 
Xue-Qian Li and Xiang Liu
hep-ph hep-ex nucl-th