V. A.  Albert and Struwe, L., ?Phylogeny and classification of Voyria (saprophytic Gentianaceae)?, Brittonia, vol. 49, pp. 466 - 479, 1997.

V. A.  Albert and Struwe, L., ?Morphological cladistics of Gentianaceae. III. Phylogeny and biogeography of the saprophytic tribe Voyrieae?, Amer. J. Bot. (Suppl.), vol. 83, p. 135, 1996.

L.  Struwe and Albert, V. A., ?Morphological cladistics of Gentianaceae. I. Phylogeny and character evolution with emphasis on woody taxa of the neotropics?, Amer. J. Bot. (Suppl.), vol. 83, p. 195, 1996.