 However, no detailed analysis of linguistic data or language classification was included in either of these surveys.Also in 1971, C. Hoffman published "Provisional Check List of Chadic Languages", which contained 17 languages divided into two sub-groups.This list was revised and amplified by Kay Williamson in a document handed out to students at the University of Ibadan, titled "Chadic languages of Nigeria" in 1972, to include 21 languages classified into three subgroups.