DJVU PDF Fromkin, V. and Gandour, J.T. 1979, "On the phonological representation of contour tones", in Linguistics of the Tibeto-Burman Area, vol. 4, no. 1, pp. 73-74. cite.

DJVU PDF Maddieson, I. 1979, "More on the representation of contour tones", in Linguistics of the Tibeto-Burman Area, vol. 4, no. 2, pp. 7-10. cite.