Columbia subject headings:
Catholic Church. Pope (1878-1903 : Leo XIII). Rerum novarum.
Christian sociology--Catholic Church.
Church and social problems--Catholic Church.
Labor--Religious aspects--Christianity.
Working class.
Harvard subject headings:
Catholic Church. Pope (1878-1903 : Leo XIII). Rerum novarum.
Christian sociology--Catholic Church.
Church and social problems--Catholic Church
Labor--Religious aspects--Christianity
Working class.
Princeton subject headings: