How to identify logos in a nonfiction book?

Logos is logic, so just look for examples of logical things in the book. Like, maybe there's a person who says that if we raise taxes by just three cents for everyone it will get us out of debt, so logically we should raise the taxes three cents. That's an example.

Are you talking about company logos, as in a little colorful picture or emblem a company uses to identify itself on commercials, ads, and stationery? You would need to use the TM, or trademark symbol.