F1⁡(α;β,β′;γ;x,y)=Γ⁡(γ)Γ⁡(α)⁢Γ⁡(γ-α)⁢∫01uα-1⁢(1-u)γ-α-1(1-u⁢x)β⁢(1-u⁢y)β′⁢ⅆ⁡u,