To be used in future
 Section A.6: Relativity-tensor notation Up Appendix A: Useful Mathematics Section A.8: Anticommutators 

A.7 Commutators

Commutators between objects (be they matrices or operators) are defined as↓ We find the following useful relations (commonly used in commutator algebra)↓↓ and
as well as
 Section A.6: Relativity-tensor notation Up Appendix A: Useful Mathematics Section A.8: Anticommutators