That's because the second author is Jeffrey Ullman (Turing Award, Neumann medal) Ullman is of the authors of several legendary computer science books Dragon B

That's because the second author is Jeffrey Ullman (Turing Award, Neumann medal) Ullman is of the authors of several legendary computer science books Dragon Book (Compilers: Principles, Techniques, and Tools) the Cinderella Book (Introduction to Automata Theory, Languages, and Computation), Green Dragon Book (Principles of Compiler Design) If you want to learn deep stuff with clarity, those old books are still the way to go.