Columbia subject headings:
Catholic Church. Pope (1878-1903 : Leo XIII). Rerum novarum.
Labor--Religious aspects--Christianity.
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:
Catholic Church. Pope (1878-1903 : Leo XIII). Rerum novarum
Labor--Religious aspects--Christianity.