Biblio
“Reports On The Conferences Of Cycles”. Washington, D.C. : Carneige Institution.
. 1929. 
“Dendrochronology And Studies In Cyclics”. University Of Pennsylvania Bicentennial Conference Proceedings. University Of Pennsylvania Bicentennial Conference Proceedings.
. 
“Dendrochronology And Studies In Cyclics”. University Of Pennsylvania Bicentennial Conference. University Of Pennsylvania Bicentennial Conference.
.