For Tribulus
Porter, D.M. 2016. Zygophyllaceae. In Flora of North America Editorial Committee. 2016. Flora of North America north of Mexico. Volume 12, Magnoliophyta: Vitaceae to Garryaceae. Oxford Univ. Press, New York, NY. 603 pp. Google Scholar
Sheahan. 2007. In Kubitzki, K., C. Bayer, and P.F. Stevens, eds. 2007. The families and genera of vascular plants. IX. Flowering plants – Eudicots – Berberidopsidales, Buxales, Crossosomatales, Fabales p.p., Geraniales, Gunnerales, Myrtales p.p., Proteales, Saxifragales, Vitales, Zygophyllales, Clusiaceae alliance, Passifloraceae alliance, Dilleniaceae, Huaceae, Picramniaceae, Sabiaceae. Springer, Berlin. 509 pp. Google Scholar