1. Abunya, Levina. 2010. “Kaakyi Verbal Morphology.” MPhil thesis, University of Ghana.
2. Adonae, A. D.2005. “Kaakyi tonology.” MPhil thesis, University of Ghana.
3. Bybee, Joan. 2003. “Cognitive Process in Grammaticalization.” In The New Psychology of Language: Cognitive and Functional Approaches to Language Structure, edited by MichaelTomasello, Vol. 2, 145–167. New Jersey: Lawrence Erlbaum.
4. Bybee, Joan, ReverePerkins, and WilliamPagliuca. 1994. The Evolution of Grammar: Tense, Aspect and Modality in the Languages of the World. Chicago: The University of Chicago Press.
5. Tense