5 Our predecessors Pius XI and Pius XII also issued decrees and exhortations to the furtherance of this cause, (6) which We confirmed with like authority and like charity when We issued Our first Encyclical Letter, Ad Petri Cathedram . (7) We think, however, and We feel sure that We will never do enough to carry out the wishes of the Divine Redeemer in this matter until all sheep are happily gathered in one fold under the leadership of one Shepherd. (8)
Source: Princeps Pastorum (Vatican.va)