^ Martin K. Spekter (1962 April) “Making a New Point, or, How About That …”, in TYPEtalks
^ Keith Houston (2013 September 24) Shady Characters: The Secret Life of Punctuation, Symbols, & Other Typographical Marks, W.W. Norton & Company, →ISBN, page 20
^ “Orbituary: Martin K. Speckter, 73, Creator of Interrobang”, in The New York Times[1], 1988 February 16