Cauwet-Marc, Anna Maria and Per Sunding. “Bupleurum salicifolium R. Brown in Buch de l’archipel Macaronésien: Taxonomie et Evolution”. Lazaroa, vol. 3, vol. 3, 1981, pp. 121-30, https://revistas.ucm.es/index.php/LAZA/article/view/LAZA8181110121A.