Wilken, B. Department Planets and Comets, Max Planck Institute for Solar System Research, Max Planck Society;
Link (Any fulltext)
Williams, D. J., Mauk, B. H., McEntire, R. E., Roelof, E. C., Armstrong, T. P., Wilken, B., et al. (1996). Electron beams and ion composition measured at Io and in its torus. Science, 274, 401-403.