1. Kalaḅarị Ekine Society: a borderland of religion and art;Robin;Africa,1963
2. Horton , ‘From fishing village to city-state’, 39–45.
3. Kay Williamson , ‘Languages of the Niger Delta’, Nigeria Magazine, no. 97 (1968), 124.
4. Long Distance Trade and States in the Niger Delta;Alagoa;J. Afr. Hist.,1970