1. Abdel Khalik K.&Bakker F. T.2007:Nasturtiopsis integrifolia(Boulos) Abdel Khalik & Bakker (Brassicaceae) a new combination andCruciata articulata(L.) Ehrend. (Rubiaceae) a new record for the Flora of Egypt. – Turk. J. Bot. (under publication).
2. Boulos L.1995:Flora of Egypt Checklist: 110–112. – Al Hadara publ. Cairo.
3. Boulos L.2000:Flora of Egypt Vol. 2: 229–242. – Al Hadara publ. Cairo.
4. The African species of Oldenlandia L. sensu Hiern et K. Schuman;Bremekamp C. E. B.;Verh. Kon. Ned. Akad. Wetensch., Afd. Natuurk., Tweed Sect.,1952
5. REMARKS ON THE POSITION, THE DELIMITATION AND THE SUBDIVISION OF THE RUBIACEAE