Geologic Map of Colorado, 1913, by R.D. George, former Colorado State Geologist. ~1:500,000 scale. High-resolution scan of the original. Digital PDF download. HM-02D
George, R. D. HM-02 1913 Geologic Map of Colorado. Colorado State Geological Survey, 1913, https://coloradogeologicalsurvey.org/publications/geologic-map-george-colorado-1913.
Geologic Map of Colorado, 1913, by R.D. George, former Colorado State Geologist. ~1:500,000 scale. High-resolution scan of the original. Digital PDF download. HM-02D