Sarah said that Benedict approved that "complete manuscript" on Nov. 25, and that the two discussed the matter in person on Dec. 3.
Gänswein said attribution of the introduction and conclusion, and Benedict's identity as a co-author, was a "misunderstanding."
Later on Jan. 14, Sarah tweeted that, while he stood by his version of events, he had requested that Fayard, the book's French publisher, acquiesce to Gänswein's request. The cardinal has insisted that "the complete text will remain absolutely unchanged."
A spokesperson for Ignatius Press told CNA Jan. 14 that while the publisher is "aware" of Gänswein's request, it stands by its statement, and considers the text a co-authored work.
"There is no doubt that Pope Benedict wrote the section 'The Catholic Priesthood;' and since Cardinal Sarah says 'the complete text will remain absolutely unchanged,' then the entries in the table of contents: 'Introduction by the Two Authors' and 'Conclusion by the Two Authors' say all we need to know," the spokesperson added.
The spokesperson told CNA that Ignatius "can't speak to what Ignatius might do if Fayard acquiesces," and that it will address that question if it becomes necessary.
Beyond the question of how the emeritus pope is credited in the work, the book has been the source of controversy because it addresses priestly celibacy while Pope Francis is said to be considering recommendations from a 2019 synod to permit the priestly ordination of some married men in the Amazon region, where there is an acute priest shortage.
Some critics have suggested that a retired pope should not have spoken on a controversial subject under consideration by the current pope. Other critics have suggested that Sarah unfairly manipulated Benedict in order to lobby Pope Francis on the subject.
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Supporters of Benedict say the retired pope has been encouraged by Pope Francis to engage on Church matters.
On Jan. 13, Andrea Tornielli, editorial director of the Vatican's communications office, praised the book.
"Ratzinger and Sarah - who describe themselves as two Bishops 'in filial obedience to Pope Francis' who 'are seeking the truth' in 'a spirit of love for the unity of the Church' - defend the discipline of celibacy and put forth the reasons that they feel counsel against changing it," Tornielli wrote.