| Umeogu, B. (2012). Symbolic universe: Towards a New Universe of Knowledge, a new Logic and a new African Philosophy. Enugu: Victojo Press. http://ai.eecs.umich.edu/cogarch0/common/theory/symbol.html | | | | |
| Umeogu, B. (1996). Principia logica. Onitsha: Mid-Field Publishers. | | | | |
| Ukagba, G. (2000). What is African philosophy. In C. Maduka (Ed.), Philosophy and logic: A primer (pp. 76-98). Benin: Department of History. | | | | |
| Stenger, F. (2012). The power of symbols in African culture. http://www.karibu-stenger.net/en/articles/power_of_symbols.shtml | | | | |
| Omenzejele, P (2000). Philosophy as a second order discipline. In C. Maduka (Ed.), Philosophy and logic: A primer (pp. 57-75). Benin: Department of History. | | | | |