Erratum to: ``The arithmetic of the product of two algebraic curves over a finite field'' (Q1090725)

[For the original paper see ibid. 98, 102-142 (1986; Zbl 0606.14026.] The main change is that the author does not have to assume that the formal Brauer group of a product surface \(X=C_ 1\times C_ 2\) is representable by a formal group. This follows from the fact, that Pic(X/k) is reduced (smooth). There is a list of further corrections.