  Lattice simulation of charmonium resonances with non-zero momentum provides
additional information on the two-meson scattering matrices. However, the
reduced rotational symmetry in a moving frame renders a number of states with
different $J^P$ in the same lattice irreducible representation. The
identification of $J^P$ for these states is particularly important, since
quarkonium spectra contain a number of states with different $J^P$ in a
relatively narrow energy region. Preliminary results concerning
spin-identification are presented in relation to our study of charmonium
resonances in flight on the Nf=2+1 CLS ensembles.
