Chomsky first referred to these Hockettian concepts in his 1962 paper The Logical Basis of Linguistic Theory (later published as Current Issues in Linguistic Theory in 1964). In it Chomsky noted that "the difference between observational and descriptive adequacy is related to the distinction drawn by Hockett (1958) between 'surface grammar' and 'deep grammar', and he is unquestionably correct in noting that modern linguistics is largely confined in scope to the former."[4]