Columbia subject headings:
Church and social problems--Catholic Church.
Labor--Religious aspects--Christianity.
Harvard subject headings:
Catholic Church. Pope (1878-1903 : Leo XIII). Rerum novarum.
Catholic Church. Pope (1922-1939 : Pius XI). Quadragesimo anno.
Church and social problems--Catholic Church
Labor--Religious aspects--Christianity
Princeton subject headings:
Church and social problems--Catholic Church.
Labor--Religious aspects--Christianity.