Discovery of Samarium, Europium, Gadolinium, and Terbium Isotopes
  Currently, thirty-four samarium, thirty-four europium, thirty-one gadolinium, and thirty-one terbium isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented. 
E. May and M. Thoennessen
nucl-ex