On a class of paracontact metric 3-manifolds
  The purpose of this paper is to classify paracontact metric $3$-manifolds $M^3$ such that the Ricci operator $S$ commutes with the endomorhism $\phi$ of its tangent bundle $\Gamma(TM^3)$. 
K. Srivastava and S. K. Srivastava
math.DG