Guy, Jacques B. M. (1992). "À propos des mois de l'ancien calendrier pascuan (On the months of the old Easter Island calendar)". Journal de la Société des Océanistes. 94 (1): 119–125. doi:10.3406/jso.1992.2611. (in French)
evertype.com
Everson, Michael (4 Dec 1998). "Table XXX - Row 30: Rongorongo"(PDF). Proposal for the Universal Character Set. Retrieved 2 February 2018.
flickr.com
See image. Other examples of petroglyphs which resemble rongorongo glyphs can be seen here and here.