2) J. E. Wertz, J. R. Bolton : "Electron Spin Resonance, Elementary Theory and Practical Applications", p. 303 (1972), (Mc Graw-Hill, New York).
3) 豊田貞治 : 燃協, 49,803(1970);横川親雄 : 燃協, 51, 1200(1972);C.L.Kwan, T.F.Yen : Anal. Chem., 51, 1225 (1979); J. G. Speight : "Analytical Methods for Coal and Coal Products", Edited by C. Karr, Jr., Vol. II, p. 86 (1978), (Academic Press, New York).