Non- ${\boldsymbol {\boldsymbol q}}$ ${\boldsymbol {\overline{\boldsymbol q}}}$ Candidates

For a review on gluonium and other non- ${\mathit {\mathit q}}$ ${\mathit {\overline{\mathit q}}}$ candidatessee PDG 2006 , Journal of Physics G33 1 (2006).See also the ``Note on scalar mesons'' in the ${{\mathit f}_{{0}}{(500)}}$ Particle Listings, our note``New charmonium-like states'' in PDG 2008 , Physics Letters B667 1 (2008), and the extensive chapter on Spectroscopy in N. Brambilla $\mathit et~al.$ (Quarkonium Working Group),The European Physical Journal C71 1534 (2011).