With Oλμ=∑jpjq⟨p||Oλ||q⟩λ−1[a†jp˜ajq]λμ, we can write ⟨ΦJM|Oλμ|ΦJ′M′⟩=∑pq⟨p|Oλμ|q⟩⟨ΦJM|a†paq|ΦJ′M′⟩, as ⟨ΦJM|Oλμ|ΦJ′M′⟩=∑jpjq⟨p||Oλ||q⟩⟨ΦJM|λ−1[a†jp˜ajq]λμ|ΦJ′M′⟩. We have suppressed the summation over quantum numbers like np,nq etc.