How do those who casually quote classics do it?

In the book Taking Time as a Friend, Li Xiaolai tells us that his father can always quote the secrets of classic works at will. The secret is in his father's notebook.

"This is a full book that has long been remembered and has been torn. Open it, and every page in it is full of allusions. To my surprise, under every allusion, there is actually a date-the date when he used this allusion in a seemingly casual conversation. Of course, in addition to the date, there are many seemingly scribbled but informative notes. For example, this allusion, sentence, anecdote, anecdote and joke can explain what the problem is and where it is used ... I will always remember my father's sentence-'You must be eager to learn things, and you can't just learn things without learning books.' "

Electronic products have many powerful functions, but we see that many people still like to write on paper notebooks with pens. I think there are at least four reasons: first, taking notes is a process of feedback, summary and thinking about what you have seen and learned; Second, even copying the original text is much more impressive than copying and pasting it in the brain; Third, paper notebooks are not affected by electricity and can be recorded at any time; Fourth, taking paper notes is more focused, and you won't suddenly get such information in the process of thinking, attracting attention to nowhere to go.