BioStor
 | Studies in the flora of Lower California and adjacent islands Alice Eastwood (1929) Proceedings of the California Academy of Sciences 18: 393-484 |
 | The genera of the Urticaceae in the southeastern United States N G Miller (1971) Journal of the Arnold Arboretum 52: 40-68 |
 | Ecological Differentiation in Some Congeneric Species of Costa Rican Flowering Plants William C Burger (1974) Annals of the Missouri Botanical Garden 61: 297-306 |