B. T.  Drew and Sytsma, K. J., ?Testing the Monophyly and Placement of Lepechinia in the Tribe Mentheae (Lamiaceae)?, issn: 0363-6445, vol. 36, pp. 1038?1049, 2011.

J. B.  Walker and Sytsma, K. J., ?Staminal evolution in the genus Salvia (Lamiaceae): Molecular phylogenetic evidence for multiple origins of the staminal lever?, Annals of Botany, vol. 100. pp. 375?391, 2007.

J. B.  Walker and Sytsma, K. J., ?Staminal evolution in the genus Salvia (Lamiaceae): molecular phylogenetic evidence for multiple origins of the staminal lever?, Annals of Botany, vol. 100, pp. 375?91, 2007.