These seem very direct and not ultra advanced, good read.
- Quantum field theory lecture notes | 56, 201, 3
- Quantum field theory bibliography | 32, 735, 19
- Quantum field theory | 219, 4k, 67
- Relativistic quantum mechanics | 95, 6k, 95
- Quantum mechanics | 170, 11k, 165
- Particle physics | 140, 19k, 291
- Physics | 276, 25k, 429
- Natural science | 0, 30k, 686
- Science | 0, 36k, 821
- Ciro Santilli's Homepage | 238, 147k, 2k
- Klein-Gordon equation | 190, 443, 1