1. J.M. Gourgout, in Secondary Ion Mass Spectrometry II, ed. By A. Benninghoven, C.A. Evans, Jr., R.A. Powell, R. Shimuzu, H.A. Storms, Springer Series in Chemical Physics, Vol. 9 ( Springer, Berlin,Heidelberg,New York 1979 ) p. 286 - 290
2. P. Williams, R.K. Lewis, C.A. Evans and P.R. Hanley, Anal. Chem. 49, 1499 (1977)