Hypergeometric transformations relating Gauss, Appell and Srivastava–Daoust functions

The object of the present paper is to obtain hypergeometric transformation formulas involving Appell's double hypergeometric function of the fourth kind F 4 and Srivastava–Daoust hypergeometric function of three variables, using Laplace-type double integral technique. Watson's summation theorem for Clausenian function 3 F 2 having unit argument is deduced as a special case. A hypergeometric transformation formula for Gauss function 2 F 1 [H. Exton, A Note on a hypergeometric transformation, Bull. Calcutta Math. Soc. 74(1979), pp. 337–340] is also corrected here.