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_{ijk}is the permutation symbol and cyclic permutations, for example 123→231→312, are always even, thus ε

_{123}=ε

_{231}=ε

_{312}=+1, but:

ε

_{132}=ε

_{213}=ε

_{321}=-1

I understand the first 2, but ε

_{321}is even, no? and also all this series is cyclic, it's not all even and....