Jordan, D. S. (April 1874). "The Flora of Penikese Island". The American Naturalist. VIII (4). Salem, Mass.: Peabody Academy of Science: 13 (193). doi:10.1086/271293. Retrieved 18 March 2009.
Jordan, D. S. (April 1874). "The Flora of Penikese Island". The American Naturalist. VIII (4). Salem, Mass.: Peabody Academy of Science: 13 (193). doi:10.1086/271293. Retrieved 18 March 2009.