Alejandro, G. J. D., Balete, I. K. C., Caagbay, J. F. C., Cruz, J. M. M. B., Narciso, C. J. C., Nazareno, D. E., . . . Uy, M. M. (2011). Polyphyly of Bikkia Reinw. [Rubiaceae] based on multi-locus sequence analysis [ITS, rps16, trnl-F], with emphasis on the endemic Bikkia philippinensis val. including its conservation status. Acta Manilana.

Alejandro, Grecebio Jonathan D., Ian Kevin C. Balete, Julian Fabian C. Caagbay, Jana May Marie B. Cruz, Christine Joy C. Narciso, Dominic E. Nazareno, Cecilia I. Banag, and Millard M. Uy. "Polyphyly of Bikkia Reinw. [Rubiaceae] Based on Multi-locus Sequence Analysis [ITS, Rps16, Trnl-F], with Emphasis on the Endemic Bikkia Philippinensis Val. Including Its Conservation Status." Acta Manilana 2011.

Alejandro, Grecebio Jonathan D., et al. "Polyphyly of Bikkia Reinw. [Rubiaceae] Based on Multi-locus Sequence Analysis [ITS, Rps16, Trnl-F], with Emphasis on the Endemic Bikkia Philippinensis Val. Including Its Conservation Status." Acta Manilana, 2011.