  An identity by Chaundy and Bullard writes 1/(1-x)^n (n=1,2,...) as a sum of
two truncated binomial series. This identity was rediscovered many times.
Notably, a special case was rediscovered by I. Daubechies, while she was
setting up the theory of wavelets of compact support. We discuss or survey many
different proofs of the identity, and also its relationship with Gauss
hypergeometric series. We also consider the extension to complex values of the
two parameters which occur as summation bounds. The paper concludes with a
discussion of a multivariable analogue of the identity, which was first given
by Damjanovic, Klamkin and Ruehr. We give the relationship with Lauricella
hypergeometric functions and corresponding PDE's. The paper ends with a new
proof of the multivariable case by splitting up Dirichlet's multivariable beta
integral.
