Wilhelm, K. MPI for Aeronomy, Max Planck Institute for Solar System Research, Max Planck Society; Department Sun and Heliosphere, Max Planck Institute for Solar System Research, Max Planck Society;
Warren, H. P., Mariska, J. T., & Wilhelm, K. (1997). Observations of Doppler shifts in a solar polar coronal hole. Astrophysical Journal, 490, L187-L190.