# hypergeometric 2f2 function reference

Could anyone suggest a reference (book or paper, no URL though) for this identity involving the ${}_2F_{2}$ hypergeometric function?

Hypergeometric functions $_pF_q$ whose parameters differ by integers are said to be contiguous; if $p\leq q+1$ then any $q+2$ distinct contiguous functions are linearly related. See the references listed in DLMF entry 16.3(ii).