∫-∞∞ⅆ⁡tΓ⁡a+t⁢Γ⁡b+t⁢Γ⁡c-t⁢Γ⁡d-t=Γ⁡a+b+c+d-3Γ⁡a+c-1⁢Γ⁡a+d-1⁢Γ⁡b+c-1⁢Γ⁡b+d-1,