[Normal ordering](Normal%20ordering.md) %%Before doing anything sort out the terminologies: What is it that people call Wick contractions, what is it that people call wick rotations, and what is Wick's theorem itself.%% %%Suggested reading for anything Wick related: pg 225 of Walter Greiner's book, Field quantization.%% #QuantumMechanics/QuantumFieldTheory