Discovery of Yttrium, Zirconium, Niobium, Technetium, and Ruthenium   Isotopes
  Currently, thirty-four yttrium, thirty-five zirconium, thirty-four niobium, thirty-five technetium, and thirty-eight ruthenium 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. 
A. Nystrom and M. Thoennessen
nucl-ex