For difficult subjects, or stuff I might not work on immediately, I go through a book or class and take COPIOUS notes. The idea is that they're good enough for

For difficult subjects, or stuff I might not work on immediately, I go through a book or class and take COPIOUS notes. The idea is that they're good enough for me to use to explain the subject to someone else; the old proverb about "You only understand something when you teach it to someone else" is really true.