The Bishop Ash Bed (Middle Pleistocene) and some older (Pliocene and Pleistocene) chemically and mineralogically similar Ash Beds in California, Nevada, and Utah - Izett, Glen A.; Obradovich, John D.; Mehnert, Harald H. (U.S. Gov. Print. Off., 1988)
Keywords: Aschentuff; USA -- Südweststaaten