A.J.H. Boerboom, Theory of the aberrations in the focusing properties of a magnetic field with one plane of symmetry, Appl. Sci. Res. B 7, 52-62 (1957)
J. Schutten, A.J.H. Boerboom, T. van der Hauw and F.L. Monterie, Precise measurement of isotope ratios with a single collector mass spectrometer, Appl. Sci. Res. B 6, 388-392 (1956)