The lessons are based on the 'Chinese-Cantonese (Toishan) Basic Course' with corrections and English translations. Here is the description of the original source from ERIC:

Chinese-Cantonese (Toishan) Basic Course.

Defense Language Inst., Washington, DC.

This seven-volume series constitutes the Defense Language Institute (Army Language School) 47-week course in the Toishan dialect of Cantonese. Beginning lessons present the tone and sound system in romanized script. Chinese characters are introduced in the fourth lesson. (See related document AL 001 479, 'Chinese Cantonese Basic Course,' for a fuller presentation of the tone and writing systems for beginning students.) Lesson units consist of oral materials (basic structures presented in both romanized form and in Chinese characters), reading and writing materials, recombination and translation exercises (in the last four volumes), and a vocabulary list. The final volume of the series, 'volume 7,' contains appended glossaries of terms of special interest to American military personnel in China.

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Additional lesson commentaries:  FOUR COUNTIES