  Establishing the CCZ-equivalence of a pair of APN functions is generally
quite difficult. In some cases, when seeking to show that a putative new
infinite family of APN functions is CCZ inequivalent to an already known
family, we rely on computer calculation for small values of n. In this paper we
present a method to prove the inequivalence of quadratic APN functions with the
Gold functions. Our main result is that a quadratic function is CCZ-equivalent
to an APN Gold function if and only if it is EA-equivalent to that Gold
function. As an application of this result, we prove that a trinomial family of
APN functions that exist on finite fields of order 2^n where n = 2 mod 4 are
CCZ inequivalent to the Gold functions. The proof relies on some knowledge of
the automorphism group of a code associated with such a function.
