In 1982 (J. Indian Acad. Math. 4, 113-119 (1982; Zbl 0509.33002), H. Exton introduced the triple hypergeometric function \(X_8\). From the Laplace integral representation given by the reviewer (loc. cit.) and a general summation result due to H. L. Manocha and H. M. Srivastava (A Treatise on generating functions (1984; Zbl 0535.33001), p. 58), two interesting summation formulae involving the function \(X_8\) are obtained. An alternative proof of the same results is also given based on the use of Cauchy products. More formulae of an analogous type could possibly be deduced similarly in the case of other hypergeometric functions of three variables.