1. Andersson, L., 1993: Pollen characteristics of the tribesCalycophylleae, Cinchoneae andHillieae (Rubiaceae). ? Nordic J. Bot.13: 405?417.
2. ?, 1996: Circumscription of the tribeIsertieae (Rubiaceae). ? Opera Bot. Belg.7: 139?164.
3. Backer, C. A., Bakhuisen Van Den Brink, R. C., 1965: Flora of Java (spermatophytes only),2. ? Groningen: Noordhoff.
4. Balfour, I. B., 1882: Diagnoses plantarum novarum et imperfecte descriptarum phanerogamarum socotrensium. Pars altera. ? Proc. Roy. Soc. Edinburgh11: 834?843.
5. - 1888: Botany of Socotra. ? Trans. Roy. Soc. Edinburgh31.