Columbia subject headings:
Dilke, Charles Wentworth, Sir, 1843-1911.
Playfair, Lyon Playfair, Baron, 1818-1898.
Harvard subject headings:
Dilke, Charles Wentworth, Sir, 1843-1911.
Playfair, Lyon Playfair, Baron, 1818-1898.
Smallpox vaccine.
Princeton subject headings: