NORM TORI OF ETALE ALGEBRAS AND UNRAMIFIED BRAUER GROUPS

Let k be a field, and let L be an etale k-algebra of finite rank. If a is an element of k(x), let X-a be the affine variety defined by N-L/k(x) = a. Assuming that L has at least one factor that is a cyclic field extension of k, we give a combinatorial description of the unramified Brauer group of X-a.