Q: It happened that I
divorced my wife and wrote to her, "I (...) with all my legal capacity divorce my wife (...) three times. She is unlawful for me and lawful for anyone else. I testify before Allah that I have made three pronouncements of divorce."
(Part No. 20; Page No. 134)
Since the husband divorced his wife and wrote the phrase mentioned in the question, this is irrevocable divorce. He explicitly stated that he made three pronouncements of divorce, and then repeated this fact in the end of the phrase. Thus, the husband can only remarry his ex-wife after she has been married to another, genuine consummation has taken place, her second marriage has been duly dissolved and her `Iddah (woman's prescribed waiting period after divorce or widowhood) has expired. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.