Note on a Class of Subsets of AG(3, q) with Intersection Numbers 1, q and n with respect to the Planes

We give a new and correct proof of a result of O. Ferri and S. Ferri (1995) on q2-caps of AG(3,q) in this paper; moreover we prove that sets of AG(3,q) of type (1,q,q+1) with respect to the planes of AG(3,q) have size at most q2 with equality if and only if is a cap