Wang, William S-Y. (1967). ”Phonological features of tone”. International Journal of American Linguistics 33 (2): sid. 93–105. doi:10.1086/464946.
Pike, Eunice V. (1986). ”Tone contrasts in Central Carrier (Athapaskan)”. International Journal of American Linguistics 52 (4): sid. 411–418. doi:10.1086/466032.
Hunter, Georgia G.; Pike, Eunice V. (2009). ”The phonology and tone sandhi of Molinos Mixtec”. Linguistics 7 (47): sid. 24–40. doi:10.1515/ling.1969.7.47.24.