15 With the head organization, the Society for the Propagation of the Faith, there are affiliated, as We have written, two other societies - the Association of the Holy Childhood and the Society of St. Peter the Apostle. Since the Holy See has made these latter organizations in a peculiar manner its own, the faithful from all over the world ought to help and maintain them by their offerings, and this in preference to other pious works whose aims are more or less specialized.
Source: Rerum Ecclesiae (Vatican.va)