Srednicki additionally merges the Lorentz-invariant measure into his asymmetric Fourier measure, d k ~ ~ = d 3 k ( 2 π π ) 3 2 ω ω , yielding [ a ^ ^ k , a ^ ^ k ′ † † ] = ( 2 π π ) 3 2 ω ω δ δ ( k − − k ′ ) .