J. C.  Barber, Francisco-Ortega, J., Santos-Guerra, A., Turner, K. G., and Jansen, R. K., ?Origin of Macaronesian Sideritis L. (Lamioideae: Lamiaceae) inferred from nuclear and chloroplast sequence datasets?, Molecular Phylogenetics and Evolution, vol. 23, pp. 293?306, 2002.

A. J.  Paton, Springate, D., Suddee, S., Otieno, D., Grayer, R. J., Harley, M. M., Willis, F., Simmonds, M. S. J., Powell, M. P., and Savolainen, V., ?Phylogeny and evolution of basils and allies (Ocimeae, Labiatae) based on three plastid DNA regions?, Molecular Phylogenetics and Evolution, vol. 31, pp. 277?99, 2004.