Quote by Terry Pratchett

Sham Harga had run a succesful eatery for many years by always smiling, never extending credit, and realizing that most of his customers wanted meals properly balanced between the four food groups: sugar, starch, grease, and burnt crunchy bits.

Please suggest source details if you know: book, page, year, online article address (url), correction (different author...), etc.. Thanks.