USGS BULLETIN 742, P. 6-14USGS BULLETIN 931-G, P. 140-152, 163-175USBM REPORT OF INVESTIGATIONS 3885.USBM REPORT OF INVESTIGATIONS 5377USGS OPEN FILE 80-87, P. 28-31USBM REPORT OF INVESTIGATIONS 3885. USBM REPORT OF INVESTIGATIONS 5377USGS CIRCULAR 252, P. 10-11