Canonical surfaces in P4 with pg = pa=5 and K2=11

In [Boh] a structure theorem for Gorenstein algebras in codimension 2 was obtained. In Section 1 of this article we give a geometric application and prove a structure theorem for good birational canonical projections of regular surfaces of general type with p(g) = 5 to P-4 (Theorem 1.6). In Section 2 we show how this can be used to analyze the moduli space of canonical surfaces with q = 0, p(g) = 5 and K-2 = 11 (Theorem 2.4).