It is known from a previous paper [3] that Katona

s Intersection Theorem follows from the Complete Intersection Theorem by Ahlswede and Khachatrian via a Comparison Lemma. It also has been proved directly in [3] by the pushing–pulling method of that paper. Here we add a third proof via a new (
k,k+1)-shifting technique, whose impact will be exploared elsewhere. The fourth and last of our proofs is a gift from heaven for Gyula

s birthday.
Mathematics Subject Classification (2000):
05C35 - 05C65 - 05D05
Presented on the Conference on Hypergraphs held in Budapest June 7–9, 2001 in Honour of Gyula Katona on the occasion of his 60th Birthday.