Trager 1964. Trager, George L. (1964). "The intonation system of American English". In Abercrombie, David; Jones, Daniel (eds.). In Honour of Daniel Jones: Papers Contributed on the Occasion of His Eightieth Birthday, 12 September 1961. Longmans, Green.
Pierrehumbert 1980. Pierrehumbert, Janet B. (1980). The Phonology and Phonetics of English Intonation (Ph.D. Thesis). Massachusetts Institute of Technology. hdl:1721.1/16065.