Describing non-$q\bar q$ candidates
  Despite the apparent simplicity of meson spectroscopy there are some states which cannot be accommodated in the usual $q\bar q$ structure. Among them there are either exotic states as the X(1600) or the recently measured charm states $D_{sJ}^*$ and X(3872) and some of the light scalar mesons. In this work we present a possible description of these states in terms of tetraquarks. 
J. Vijande, F. Fernandez, A. Valcarce