Yao-English Dictionary, by Sylvia Lombard , edited by Herbert C. Purnell Jr. (Data Paper: no.69, Southeast Asia Program, Department of Asian Studies, Cornell University, Ithaca, New York, Jan 1968). Typescript.
An English-Yao Dictionary, by Sylvia Lombard with Richard D. Cushman & Herbert Purnell Jr. (Cornell Yao Project, Ithaca, New York, 1970). Typescript.