IS-21 Bibliography and Index of Colorado Geology, 1983 Download Publication Details The IS-21 bibliography contains Colorado geology citations that are cross-indexed by subject, county, and rock type. 127 pages. Digital PDF download. IS-21D Colorado is one of the few states with geological bibliographic coverage extending back as far as 1875. The first bibliography is CGS Bulletin 37 (B-37) covering the years 1875 through 1974; the next, Bulletin 45 (B-45) covers 1975 through 1980; Information Series 19 (IS-19) covers 1981-1982, and finally this publication covering 1983. A later publication completes the series, Information Series 30 (IS-30) extends coverage through 1989. Citations in all these publications are included in the American Geological Institute GEOREF database. Citations American Geological Institute. “IS-21 Bibliography and Index of Colorado Geology 1983.” Bibliography. Information Series. Denver, CO: Colorado Geological Survey, Department of Natural Resources, 1987. https://doi.org/10.58783/cgs.is21.ujoz4258. CGS Publications. https://coloradogeologicalsurvey.org/publications/bibliography-colorado-geology-1983/.