For the angular momentum operators L x = y p z − z p y, etc., one has that [ L x , L y ] = i ℏ ℏ ϵ ϵ x y z L z , where ϵ ϵ x y z is the Levi-Civita symbol and simply reverses the sign of the answer under pairwise interchange of the indices. An analogous relation holds for the spin operators.