Iniguez, Jose M. 2006. ?Landscape Fire History And Age Structure Patterns In The Sky Islands Of Southeastern Arizona?. School Of Natural Resources. School Of Natural Resources. University of Arizona. http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=1144189411&sid=5&Fmt=2&clientId=43922&RQT=309&VName=PQD.

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.

Elliott, Deborah. 1979. ?The Stability Of The Northern Canadian Tree Limit: Current Regenerative Capacity?. Geography. Geography. University of Colorado. http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=751614031&sid=5&Fmt=1&clientId=43922&RQT=309&VName=PQD.