Let X ⊂ Pkn be an irreducible
projective variety. Let B = k[x0,…,xn] and let P ⊂ B be the homogeneous prime
ideal of X generated by ht(p) + 1 elements and let A = B∕P be the homogeneous
coordinate ring of X. The following are equivalent: (1) A(p) is a complete intersection
for all homogeneous prime ideals p in A of height 1; (2) P2 is primary: (3) Pi is
primary for all integers i > 0.