Columbia subject headings:
United States--History--Civil War, 1861-1865--Causes.
United States--History--Civil War, 1861-1865.
Harvard subject headings:
United States--History--Civil War, 1861-1865
United States--History--Civil War, 1861-1865--Causes.
Princeton subject headings:
United States--History--Civil War, 1861-1865--Causes.
United States--History--Civil War, 1861-1865.