Can you suggest any source available on internet which may be particularly helpful for those studying/brushing up knowledge of classical or quantum field theory without help of any teacher or friend? Some calculations are at first not so straightforward and there are many types of calculations requiring special tricks and caution to get the correct answer. Most books do not show all the intermediate steps of calculations perhaps because such books are meant to be used under guidence of teachers who are supposed to help the students by showing detailed steps in the classroom. But those with practically no such help face difficulty. Is there any help on internet for such students?