For Thymus
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
Jalas J. 1972. Thymus. In Tutin, T.G., V.H. Heywood, N.A. Burges, D.M. Moore, D.H. Valentine, S.M. Walters, and D.A. Webb. 1972. Flora Europaea. Volume 3. Cambridge, England. Google Scholar