3 literature references:

Author: Liu, T.S.
Year: 1971
Title: A monograph of the genus Abies
Source: Dept. of Forestry, National Taiwan University, Taipei
Author: Wrobel, M. & Creber, G.
Year: 1996
Title: Elsevier's dictionary of plant names
Source: Elsevier, Amsterdam
Author: Farjon, A.
Year: 2010
Title: A Handbook of the World's Conifers
Source: E.J. Brill, Leiden