Potassium-argon dates and the Cenozoic mammalian chronology of North America Evernden, J. F. ; Savage, D. E. ; Curtis, G. H. ; James, G. T. Abstract Publication: American Journal of Science Pub Date: February 1964 DOI: 10.2475/ajs.262.2.145 Bibcode: 1964AmJS..262..145E