One should carefully avoid the following types of statements: [...] 4. Imperative In the place of the statement: To form the past tense, drop the infinitive '-l' and add '-t'. Use: The infinitive suffix '-l' and the past-tense suffix '-t' are added to the stem. It is the traditional practice in textbooks to use imperative expressions in the form of 'rules' to describe the structure of a language. These are to be avoided completely.
- Nida (1949), a pag.241-242