On every page you can see some buttons, that will help you to navigate and do exercises. Navigation buttons: - back - go to the previous page; - next - go to the next page; - last unit - go to the previous unit; - next unit - go to the next unit; - explanation/exercises - go to the explanations/exercises of the unit; - contents - go to the contents (from wich you can go to the unit you wish); - exit - exit the document; - question - go to this help text. Buttons in exercises: - check -.
