28 Knowing what power our Lady's Rosary possesses, not a few of Our Predecessors took special care to spread the devotion throughout the countries of the East-in particular Eugene IV in the Constitution "Advesperascente" issued in 1439, and later Innocent XII and Clement XI. By their authority, privileges of wide extent were granted to the Order of Preachers in favor of this project. The hoped-for results were forthcoming, thanks to the energetic activity of the brethren of that Order, result to which many a bright record bears witness, although time and adversity have since raised great obstacles in the way of further progress. Yet even today the same zeal for the Rosary devotion which We cited at the beginning of this Letter still fills the hearts of great numbers in those lands-a fact which, We trust, will be as useful in the realization of Our hopes as it was in raising them.
Source: Adiutricem (Vatican.va)