Excellent series. My daughter is for 2 years in classes of 36 students and do not hear / understand the whole course. And so, to review the progress quietly, I took the book that explains step by step clearly what there is to understand, and emphasizes that it is important to remember. It allows to play down the difficult to understand oral course in the cacophony and resume quietly at home! This second allowed him to spend an average of 11 to an average of 15. I expect the same course of it !!!!