  In 2012, we investigated the possible molecular states composed of two
charmed mesons [Phys.Rev. D 88, 114008 (2013), arXiv:1211.5007 [hep-ph](2012)].
The $D^*D$ system with the quantum numbers of $I(J^P)=0(1^+)$ was found to be a
good candidate of the loosely bound molecular state. This state is very close
to the $D^*D$ threshold with a binding energy around 0.47 MeV. This prediction
was confirmed by the new LHCb observation of $T_{cc}^+$ [see Franz Muheim's
talk at the European Physical Society conference on high energy physics 2021].
