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;
McDiarmid, D. R., & Nielsen, E. (1987). Stimultaneous observation of monochromatic and variable period geomagnetic pulsations. Journal Geophysical Research, 92, 4445.