ABSTRACT. Explicit and implicit product integral techniques are used to represent a solution U to the abstract system: £/i2(x, y) = AU(x, y); U(x, 0) = p = U(0, y). The coefficient A is a closed linear transformation defined on a dense subspace D(A) of the Banach space X and the point p in D(A) satisfies the condition that WA'pW < S'(i\)3/2 for all integers i > 0 and some S > 0. The implicit technique is developed under the additional assumption that A generates a strongly continuous semigroup of bounded linear transformations on X. Both methods provide representations for the Jq Bessel function.