# §16.13 Appell Functions

The following four functions of two real or complex variables and cannot be expressed as a product of two functions, in general, but they satisfy partial differential equations that resemble the hypergeometric differential equation (15.10.1):

16.13.1,
16.13.2,
16.13.3,
16.13.4.

Here and elsewhere it is assumed that neither of the bottom parameters and is a nonpositive integer.