- The words "legal" and "valid" should be exchanged in the last paragraph of Lemma 7 on p. 604.
- Lemma 3(1) should read "h(\Phi(\beta S)) is a prefix of h(\Phi(\beta L)) and h(\Phi^2(\beta S)) is a prefix of h(\Phi^2(\beta L))" and the first paragraph of the proof should be modified accordingly.
- In the proof of Lemma 3, the first sentence of the second paragraph should read, "Since h(S) is a suffix of h(L), \overline(h(S)) is a suffix of h(SL), and so \overline(h(SL)) is a suffix of h(SLL)."
- in Lemma 1, instead of a,b,c \in \Sigma, it should be a,c \in \Sigma, b \in \Sigma^*
- in the proof of Lemma 5 (twice), the proof of Theorem 6, and the example: (k-2)(N-2+mk\Delta) should be instead (k-1)(N-2+mk\Delta).
- In the first paragraph of Section 4, we state that for a uniform morphism h, if a word is markable then its extensions are markable. Wojciech Wegrzynek has pointed out to us that this claim is not correct. However, he has also shown that it becomes correct with the additional condition that h(0) and h(1) end with different letters. Since this is the case for all morphisms h_n that are used in the paper, the results remain correct.