References
For Urtica
Boufford, D.E. 1997. Urticaceae. In Flora of North America Editorial Committee. 1997. Flora of North America north of Mexico. Volume 3, Magnoliophyta: Magnoliidae and Hamamelidae. Oxford Univ. Press, New York, NY. 590 pp. Google Scholar
Friis, I. 1993. Urticaceae. Pp. 612-630 In Kubitzki, K., J.G. Rohwer, and V. Bittrich, eds. 1993. The families and genera of vascular plants. II. Flowering plants – Dicotyledons – Magnoliid, Hamamelid and Caryophyllid families. Springer, Berlin. 653 pp. Google Scholar
Grosse-Veldmann, B., and M. Weigend. 2017. The geometry of gender: hyper-diversification of sexual systems in Urtica L. (Urticaceae). Cladistics (2017): 1-20. Google Scholar
Henning, T, D. Quandt, B. Grosse-Veldmann, A. Monro, and M. Weigend. 2014. Weeding the nettles II: a delimitation of “Urtica dioica L.” (Urticaceae) based on morphological and molecular data, including a rehabilitation of Urtica gracilis Ait. Phytotaxa 162: 61-83. Google Scholar
Woodland, D.W. 1982. Biosystematics of the perennial North American taxa of Urtica. II. Taxonomy. Syst. Bot. 7: 282-290. Google Scholar
Woodland, D.W., I.J. Bassett, C. Crompton, and S. Forget. 1982. Biosystematics of the perennial North American taxa of Urtica. I. Chromosome number, hybridization, and palynology. Syst. Bot. 7: 269-281. Google Scholar