References for Callitrichaceae
Fassett, N.C. 1951. Callitriche in the New World. Rhodora 53:137-155, 161-182, 185-194, 209-222.
Rubtzoff, R. 1969. Notes on the Callitriche in western North America. Wasmann J. Biol. 27:103-114.

Source for the Reference Lists

George W. Douglas, Del Meidinger and Jim Pojar. 1998-2002. Illustrated Flora of British Columbia.