@article{P077.018, author={Feys, J.P.R. and De Mey, G. and Claeys, E.G. and Van Der Kelen, G.P.}, title={The field within a commercial EI/FI Source of a mass spectrometer}, journal={Zeitschrift fur Naturforschung}, year={1977}, month={8}, volume={32}, pages={768-774}, }