Ofure, Ikoyo-Eweto Evarista (2016-01-01). "A proposed order of historical emergence of Esan speech varieties". Dialectologia et Geolinguistica. 24 (1): 145–156. doi:10.1515/dialect-2016-0008. ISSN0942-4040.
Egbefo, Dawood Omolumen (2017). "The role of agriculture in economic development and inter-group relations in pre-colonial esan economy". Research Journal of Humanities and Social Sciences. 8 (2): 139. doi:10.5958/2321-5828.2017.00020.1. ISSN0975-6795.
Ofure, Ikoyo-Eweto Evarista (2016-01-01). "A proposed order of historical emergence of Esan speech varieties". Dialectologia et Geolinguistica. 24 (1): 145–156. doi:10.1515/dialect-2016-0008. ISSN0942-4040.
Egbefo, Dawood Omolumen (2017). "The role of agriculture in economic development and inter-group relations in pre-colonial esan economy". Research Journal of Humanities and Social Sciences. 8 (2): 139. doi:10.5958/2321-5828.2017.00020.1. ISSN0975-6795.