María Gabriel y Galán, J.; Prada, C.; H. Rolleri, C.; Lahoz-Beltrá, R.; Martínez-Calvo, C. Biometry of Stomata in Blechnum Species (Blechnaceae) With Some Taxonomic and Ecological Implications for the Ferns. Rev. Biol. Trop. 2011, 59, 403–415.