The text typically refers to a widely used academic textbook titled Quantum Chemistry
Mastering the Microscopic: A Guide to R.K. Prasad’s Quantum Chemistry
Pay close attention to the chapters on Group Theory, as this is how chemists predict if a reaction is "allowed" or "forbidden."
You can find extensive excerpts and uploaded versions on sites like Scribd - Quantum Chemistry by R.K. Prasad Supplemental Learning: For visual learners, pairing this text with the Chemistry LibreTexts Quantum Modules