/** Trilogarithm. */
DECLARE_FUNCTION_1P(Li3)
-/** Gamma function. */
+/** Riemann's Zeta-function. */
+DECLARE_FUNCTION_1P(zeta)
+//DECLARE_FUNCTION_2P(zeta)
+
+/** Gamma-function. */
DECLARE_FUNCTION_1P(gamma)
+/** Psi-function (aka polygamma-function). */
+//DECLARE_FUNCTION_1P(psi)
+DECLARE_FUNCTION_2P(psi)
+
/** Factorial function. */
DECLARE_FUNCTION_1P(factorial)