Verbatim text: Christensen, C. 1938. Azollaceae. In: F. Verdoorn, ed. 1938. Manual of Pteridology. The Hague. P. 550.
Author: Christensen, C.
Year: 1938
Title: Azollaceae
Editor: Verdoorn, F.
Source: Manual of Pteridology
Journal: The Hague. P
Pages: 550