This paper establishes a rigorous, constructive two-way equivalence between the classical explicit analytic solutions of a wide class of integral equations (including Fredholm, Volterra, nonlinear Hammerstein, singular, stochastic, fractional, exterior, and total integral equations) and solutions represented by a single unified series derived from an integral-algebraic closure. The forward direction proves that every analytic solution can be expanded in a series u =u0+ (Φm) 1/pmωkmpmψm, m∈I where ψm are basis functions of the linearized integral operator, Φm are elements of the closure built from explicit combinatorial coefficients: Gamma ratios for fractional integrals, Gaunt coefficients (Wigner 3-j symbols) for orthogonal polynomial expansions, Hilbert transform matrix entries (±2) for Chebyshev bases, and chaos contraction coefficients r! nrmr for Wiener–Itˆo integrals. The series converges uniformly on compact sets (or in L2 for stochastic cases). The backward direction shows that any function represented by such a series satisfies a nonzero integral polynomial that is equivalent (up to a constant factor) to the original equation. Consequently, every classical special function (60+ examples, from elementary functions to Mittag-Leffler and Lambert W) admits a unified series representation. Moreover, all tested integral equations (60+ examples) are verified to satisfy the equivalence. The paper provides complete, self-contained proofs of the equivalence theorem (each theorem with at least 4 steps, key theorems with 8–14 steps), exhaustive verification, explicit combinatorial coefficient formulas, and algorithmic implementations (pseudo-code, convergence analysis, interval arithmetic). All previously open problems concerning representability of integral equation solutions are resolved and turned into theorems. This revised edition incorporates rigorous completions of all partial proofs, including the analyticity of eigenfunctions, the Puiseux expansion convergence, the Wiener–Hopf solution, and the explicit bounds for the homotopy radius.
shifa liu (Wed,) studied this question.