On the general structure of Ricci collineations for type B warped   spacetimes
  A complete study of the structure of Ricci collineations for type B warped spacetimes is carried out. This study can be used as a method to obtain these symetries in such spacetimes. Special cases as 2+2 reducible spacetimes, and plane and spherical symmetric spacetimes are considered specifically. 
J.L. Flores, Y. Parra and U. Percoco