Einstein observatory catalog of IPC x-ray sources  vol. 4 
Einstein Catalog Committee                                 
 - Cambridge  Smithsonian Astrophysical Observatory  1990 
 - iii, 528p. 
 - v.4 .
<br/><br/><label>Subjects--Topical Terms: </label><br/>Catalog-Imaging propotional counter.<br/>X-Ray sources
<br/><br/><label>Universal Decimal Class. No.: </label>017:52-73  / EIN.4