1. Osborn, Albert S., Questioned Documents. 2nd Ed. (Albany: Boyd PrintingCo,1929), p168.
2. Hilton, Ordway, Scientific Examination of Questioned Documents. Revised ed. (New York: Elsevier/North-Holland,1982), p144.
3. Osborn, Albert S., Questioned Documents. 2nd Ed. (Albany: Boyd PrintingCo.1929), p191.
4. Masson, Janet Fenner, A Look at the Hand Lettering of Draftsmen. Presented at themeeting of the American Society of Questioned Document Examiners (San Jose, 1990).