Keller, H. U. Department Planets and Comets, Max Planck Institute for Solar System Research, Max Planck Society; MPI for Aeronomy, Max Planck Institute for Solar System Research, Max Planck Society;
Keller, H. U. (2005). Comet Halley observed during the ESA Giotto fly-by. IAU Symposia, 13(A9), 724-724.