D+s0(2317)-D0(2308) mass difference as evidence for tetraquarks -: art. no. 162002

We argue that the anomalously small mass difference between the D-s0(+)(2317) and the recently observed D-0(2308) (Belle) state is the first smoking gun experimental evidence of their tetraquark [cq((qq) over bar)] structure. The recently reported D-sJ(+)(2632) (SELEX) state completes the low-lying nonexotic tetraquark spectrum, as predicted by 't Hooft's instanton-induced effective quark interaction.