Multi-volume works

Frey, W. (ed.), 2009-. Syllabus of Plant Families / A. Engler's Syllabus der Pflanzenfamilien. 13th ed. Gebrüder Borntraeger.

Articles

Stech, M. & Frey, W., 2008. A morpho-molecular classification of the mosses (Bryophyta). Nova Hedwigia 86 (1-2), Feb 2008: 1-21. ≡