This information is not only difficult, but also very concentrated, so if your head feels tired – don’t violate it, put this text away. Actually, it’s an universal rule: if your eyes are tired, don’t force them, close them, respect them, let them rest, and then they will serve you well. Read papers with good light.

 it's 187.4 MB of text & picutes in the BOOK (even more, if you click on further)