Aaron David Pan & Bonnie F. Jacobs: The earliest record of the genus Cola (Malvaceae sensu lato: Sterculioideae) from the Late Oligocene (28–27 Ma) of Ethiopia and leaf characteristics within the genus. Plant Systematics and Evolution, 2009, 283. vsk, nro 3–4, s. 247–262. Springer Vienna. doi:10.1007/s00606-009-0225-1Artikkelin verkkoversio. Viitattu 17.12.2012. (englanniksi)
Cola Notes Malvaceae.info. Viitattu 17.12.2012. (englanniksi)
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Aaron David Pan & Bonnie F. Jacobs: The earliest record of the genus Cola (Malvaceae sensu lato: Sterculioideae) from the Late Oligocene (28–27 Ma) of Ethiopia and leaf characteristics within the genus. Plant Systematics and Evolution, 2009, 283. vsk, nro 3–4, s. 247–262. Springer Vienna. doi:10.1007/s00606-009-0225-1Artikkelin verkkoversio. Viitattu 17.12.2012. (englanniksi)