^ abcGlime, Janice M. 2007. Bryophyte Ecology. Volume 1. Physiological Ecology. Ebook sponsored by Michigan Technological University and the International Association of Bryologists. accessed on 21, Apr. 2012 at <http://www.bryoecol.mtu.edu/>. pp.17-26
^Peter Robert Bell,Alan R. Hemsley (2001) Green Plants: Their Origin and Diversity. Cambridge University Press p.104