p4 Example 3.5: "three critical pairs" should read "three critical pairs (except symmetric one)". (reported by Teppei Saito)

p6 Proof of Lemma 3.12, (4): "by Lemma 3.11(b) where P = { ε }" is unnecessary. (reported by Teppei Saito)

p26 "[Ohl02]" should be corrected to: Enno Ohlebusch. Modular Properties of Composable Term Rewriting Systems. PhD thesis, Universität Bielefeld, 1994. (reported by Fuyuki Kawano)