- Greenman, J.M. 1898. Contributions from the Gray Herbarium of Harvard University, New Series, No. XIV. 1. Revision of the Mexican and Central American species of Galium and Relbunium. 2. Diagnoses of new and critical Mexican Phanerogams. Proceedings of the American Academy of Arts and Sciences 33(25): 455–470. DOI: 10.2307/20020832 . BHL.