J. Mytnik-Ejsmont, P. Rutkowski, and D. L. Szlachetko, “Five new species of Pachygenium (Schltr.) Szlach., R. González & Rutk. (Spirantheae, Cyclopogoninae, Orchidaceae) from Brazil”, biorc, no. 11-12, pp. 3–8, Dec. 2008.