Hν(1)⁡(z)Hν(2)⁡(z)}=(2π⁢z)12⁢ⅇ±ⅈ⁢ω⁢(∑k=0ℓ-1(±ⅈ)k⁢ak⁡(ν)zk+Rℓ±⁡(ν,z)),