For Teucrium
Harley et al. 2004. In Kadereit, J.W. 2004. The families and genera of vascular plants. VII. Flowering plants – Dicotyledons – Lamiales (except Acanthaceae including Avicenniaceae). Springer, Berlin. 478 pp. Google Scholar
McClintock, E., and C. Epling. 1946. A revision of Teucrium in the New World, with observations on its variation, geographical distribution and history. Brittonia 5: 491-510. Google Scholar
Shinners, L.H. 1963. The varieties of Teucrium canadense (Labiatae). Sida 1(3): 182-183. Google Scholar