In fact, what you want to ask is how to know that this is a three-buy. Entanglement theory provides a way to capture "three buys" as much as possible. You need to read this book n times. Entanglement theory is just a remnant or just a preface. If you are really interested, you should go your own way.
The so-called: entanglement refers to and heaven remains our neighbourhood, only for the right person.