2) Listgarten, M.A. : Electron microscopic observations on the bacterial flora of acute necrotizing ulcerative gingivitis. J. Periodontol., 36 : 328-339, 1965.
3) Heylings, R.T. : Electron microscopy of acute ulcerative gingivitis (Vincent's type). Br. Dent. J., 122 : 51-56, 1967.
4) Rosebury, T. and Foley, G.: Experimental Vincent's infection. J. Am. Dent. Assoc., 26 : 1798-1811, 1939.
5) Hampp, E.G. and Mergenhagen, S.E. : Experimental infections with oral spirochetes. J. Infect. Dis., 109 : 43-61, 1961.