CROSBY 1969 COLO SCH MINES QRTLY VOL 64 NO 1 P 169-194FRYKLUND (WITH A SECTION BY WEIS) 1964 USGS PROF PAPER 445RANSOME AND CALKINS 1908 USGS PROF PAPER 62 203PUMPLEBY AND JONES 1923 USGS BULL 732 156PGRIGGS 1952 USGS OPEN FILE REPT 108P 23 PLS GLGY NOTES CNY