The pope's outreach to other Christian churches including his decision to make it easier for members of the 70 million-strong Anglican Communion to convert to Catholicism was interpreted by some people as an attempt to poach faithful from rival flocks.

WSJ: Pope Defended Church Teachings

Other major Christian churches have not only officially endorsed the bill but have published learned treatises explaining their position.

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One is Leo Scheffczyk, an aged theologian from Munich, the other, Walter Kaspar, at present number two in the Vatican department which deals with the separated Christian Churches.

BBC: Analysis: Pope strengthens rule of Rome