At the origin, this textbook was designed as a support to a course proposed to students in their first year of Master at the Universit? catholique de Louvain. However, the majority of the sections could already be followed by undergraduate students. Quizzes including questions that provide an overview of the matter covered in the different chapters are available online. If you are able to answer all of them, this likely shows that you have not missed the most important elements of the discussion.