For Fermions, the fundamental anti-commutation relations are defined as:
An introduction to pairing phenomena. Part II: Relativistic Many-Particle Systems
: Fetter and Walecka rely strictly on canonical operator formalism and equations of motion. Modern research extensively uses functional path integrals (Grassmann variables for fermions) to derive Feynman rules faster.
: Developing the mathematical grammar to handle systems where particle numbers fluctuate or are too massive to track individually.
