A monograph the genus Dryopteris :
Christensen, Carl.
A monograph the genus Dryopteris : Part, I, II. - Copenaguel 1913-20 - The Tropical American Pinnatifid - Bipinatifid Species .
A monograph the genus Dryopteris : Part, I, II. - Copenaguel 1913-20 - The Tropical American Pinnatifid - Bipinatifid Species .