Typo! (Z/nZ)× should be (Z/nZ)\0 on pages 24 and 25.
Typo! In Lemma 2.17 on page 30 the inequality ≤ should be <, and in the proof of Proposition 2.18 in the top two lines on page 31 the inequalities involving the quantities in absolute value should be changed: the inequality ≤ should be <, and the inequality > should be ≥.
Typo! In the proof of Proposition 2.29 on page 40 the inequality < k/2 should be ≤ k/2.
