The <inline-formula><tex-math id="M1">\begin{document}${{ ss \bar s \bar s}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="//www.macurncorp.com/hepnp/article/app/id/f0a1067d-6de8-415c-ac42-c912be3cd694/CPC-2019-0325_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="//www.macurncorp.com/hepnp/article/app/id/f0a1067d-6de8-415c-ac42-c912be3cd694/CPC-2019-0325_M1.png"/></alternatives></inline-formula> tetraquark states and the structure of <i>X</i>(2239) observed by the BESIII collaboration -

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