A local anharmonic treatment of vibrations of methane
  The stretching and bending vibrations of methane are studied in a local anharmonic model of molecular vibrations. The use of symmetry-adapted operators reduces the eigenvalue problem to block diagonal form. For the 44 observed energies we obtain a fit with a standard deviation of 0.81 cm$^{-1}$ (and a r.m.s. deviation of 1.16 cm$^{-1}$). 
R. Lemus, F. Perez-Bernal, A. Frank, R. Bijker and J.M. Arias   (ICN-UNAM, Mexico and Sevilla, Spain)