Australian opera singer; best known by her stage name, Nellie Melba, born Helen Porter Mitchell
Helen Porter Armstrong
- "Melba, Madame (Helen Porter Armstrong)," in The Dictionary of Australasian Biography (p. 318), by Philip Mennell, London: Hutchinson & Co. (1892)
- "Melba, Nellie," in Encyclopædia Britannica (11th ed., 1911)
- "Melba, Madame," in Encyclopædia Britannica (12th ed., 1922)
- "Melba, Nellie," in The Nuttall Encyclopædia, (ed.) by James Wood, London: Frederick Warne and Co., Ltd. (1907)
- "Melba, Nellie (Mitchell)," in Collier's New Encyclopedia, New York: P. F. Collier & Son Co. (1921)