Columbia subject headings:
Helmholtz, Anna von, 1834-1899--Correspondence.
Helmholtz, Hermann von, 1821-1894.
Wagner, Cosima, 1837-1930--Correspondence.
Harvard subject headings:
Helmholtz, Anna von, 1834-1899--Correspondence.
Helmholtz, Hermann von, 1821-1894.
Wagner, Cosima, 1837-1930--Correspondence.
Princeton subject headings:
Helmholtz, Anna von, 1834-1899--Correspondence.
Helmholtz, Hermann von, 1821-1894.
Wagner, Cosima, 1837-1930--Correspondence.