Nielsen, E. MPI for Aeronomy, Max Planck Institute for Solar System Research, Max Planck Society; Department Planets and Comets, Max Planck Institute for Solar System Research, Max Planck Society;
Lambert, M., Nielsen, E., & Bruns, G. (1992). Conjugate observations of the auroral ionosphere using multi narrow-beam riometers. Annales Geophysicae, 10, 566-576.