Discovery of Tantalum, Rhenium, Osmium, and Iridium Isotopes
  Currently, thirty-eight tantalum, thirty-eight rhenium, thirty-nine osmium, and thirty-eight iridium, 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. 
R. Robinson and M. Thoennessen
nucl-ex