Columbia subject headings:
Jacob, Max, 1876-1944. Correspondence.
Maritain, Jacques, 1882-1973--Correspondence.
Harvard subject headings:
Jacob, Max, 1876-1944. Correspondence.
Maritain, Jacques, 1882-1973--Correspondence.
Princeton subject headings:
Jacob, Max, 1876-1944. Correspondence. Selections
Maritain, Jacques, 1882-1973--Correspondence.