Sidney Lau (劉錫祥) wrote a series of textbooks in the 1970s, for teaching Anglophones to speak Cantonese. The textbooks were initially used for teaching western expatriates working in the Hong Kong Police Force and other government bodies. Later the texts were used as a basis for a radio teaching programme for foreigners. The books introduced Lau's own romanisation system which differs from the Yale system by using superscripted numbers and symbols to indicate the tones of the words. The system is one of three romanisation systems still in use in Hong Kong.
Lau's A practical Cantonese-English dictionary was published by the Hong Kong government in 1977, and reviewed favorably by Dew in the Journal of Chinese Linguistics.
Despite their age, the books are still very popular, being one of the few comprehensive courses teaching spoken Cantonese (as opposed to written Chinese and spoken Mandarin, which are significantly different).