1. Orature and Yoruba Riddles
2. Yoruba Art and Language
3. Hays B. (2017) ‘Scientists say humans may have triggered desertification of the Sahara’, United Press International, 14 March .
4. American Geophysical Union (1999) ‘Sahara's abrupt desertification started by changes in earth's orbit, accelerated by atmospheric and vegetation feedbacks’, Science Daily, 12 July .