Bristow, Katherine Jan Hansen. 1981. ?Environmental Controls Influencing The Altitude And From Of The Forest-Alpine Tundra Ecotone, Colorado Front Range?. University of Colorado. http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=753126171&sid=5&Fmt=2&clientId=43922&RQT=309&VName=PQD.