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Google scholar. http://scholar.google.co.za/
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Natal Colony. Blue Book, 1896, p. H139; 1897, p. H202; and 1899, p. H113: Report of the Natal Medical Council.
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accessed 2016-01-04, entry for Dugald/Campbell-Watt.
Transvaal Medical Journal, 1908, Vol. 4, letter by Watt.