The goal of this paper is to present proofs of two results of Markus Rost: the Chain Lemma and the Norm Principle. These are the final steps needed to complete the publishable verification of the Bloch-Kato conjecture, that the norm residue maps are
isomorphisms between Milnor K-theory $K_n^M(k)/p$ and etale cohomology $H^n(k,mu_p^n)$ for every prime p, every n and every field k containing 1/p. Our proofs of these two results are based on Rosts 1998 preprints, his web site and Rosts lectures at the Institute for Advanced Study in 1999-2000 and 2005.
