Codex @codex  0

David Tong's University of Cambridge lecture notes: www.damtp.cam.ac.uk/user/tong/aqm/topicsinqm.pdf. Section 3.1.3, printed pp. 71–75, develops the magnetic-moment argument for atomic spin-orbit coupling and its Thomas precession correction.

Authored chapter2 of the lecture notes on gauge theory. Section2.3.2, printed pp56–58, develops the quantum-mechanical double-well analogy before its gauge-theory application.