Lie Symmetries and Preliminary Classification of Group-Invariant   Solutions of Thomas equation
  Using the basic prolongation method and the infinitesimal criterion of invariance, we find the most general Lie point symmetries group of the Thomas equation. Looking the adjoint representation of the obtained symmetry group on its Lie algebra, we will find the preliminary classification of its group-invariant solutions. This latter provides a new exact solutions for the Thomas equation. 
A. Ouhadan and E. H. El Kinani