- Textbooks contain a comprehensive standard scope and sequence for a set of courses focused on the languages learning.
- Textbooks contains a structured, clear, and logical progression of topics.
- Textbooks are divided into themes, each theme contains two units, each unit contains different topics, and each topic is divided into smaller sections: introduction, form, example, use, summary, related, exercises.
(See https://open.books4languages.com/english-a1-grammar/chapter/cardinal-numbers/).
It must be taken into account, when developing the units, that a unit in levels A is designed to be studied in approximately one week, and two weeks in the case of levels B and C (one unit consists of all the topics for each of the 5 books).