Estes, Eugene Todd. 1969. ?The Dendrochronology Of Three Tree Species In The Central Mississippi Valley?. Botany. Botany. Southern Illinois University. http://ezproxy.library.arizona.edu/login?url=http://proquest.umi.com/pqdweb?did=755447421&sid=11&Fmt=1&clientId=43922&RQT=309&VName=PQD.