.0 Lambert, R.S.J., 1971, The pre-Pleistocene Phanerozoic time-scale--A review, in Part I of the Phanerozoic time-scale--A supplement: Geol. Soc. London Spec. Pub. no. 5, p. 9-34. Langenheim, R.L., Jr., 1952, Pennsylvanian and Permian stratigraphy in Crested Butte quadrangle, Gunnison County, Colorado: Am. Assoc. Petroleum Geologists Bull., v. 36, no. 4, p. 543-574. Tweto, Ogden, 1979, Geologic Map of Colorado: U.S.Geol. Survey, Special Geologic Map.