References for Charles 4th Marquess, 3rd Duke, 2nd Duke, 1st Earl Douglas * of Queensberry * of Queensberry * of Dover * of Sallway

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Sir B.Burke: A Genealogical History of the Peerages and Knightages of the British Empire. London, 1953
Sir B.Burke: Burke's Peerage and Baronetage. London, 1999