Origin of the woody macaronesian Sempervivoideae and the phylogenetic position of the East African species of Aeonium Mes, T.H.M.; Van Brederode, J.; 't Hart, H. Botanica Acta 109(6): 477-491 1996 0932-8629 10.1111/j.1438-8677.1996.tb00601.x https://eurekamag.com/research/009/930/009930960.php