Conformally flat pseudo Riemannian Homogeneous Ricci Solitons 4 spaces
  We consider four dimensional conformally flat homogeneous pseudo Riemannian manifolds. According to forms (Seger types) of the Ricci operator, we provide a full classification of four dimensional pseudo Riemannian conformally flat homogeneous Ricci solitons. 
Mohamad Chaichi and Yadollah Keshavarzi
math.DG