Christenhusz, Maarten J. M., Xian-Chun Zhang, and Harald Schneider
A linear sequence of extant families and genera of lycophytes and ferns
Journal/Book Name, Vol. No.:
Phytotaxa, vol. 19
Available online at http://www.mapress.com/phytotaxa/content/2011/f/pt00019p054.pdf
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