Schlegel, K. MPI for Aeronomy, Max Planck Institute for Solar System Research, Max Planck Society;
Link (Any fulltext)
Haldoupis, C., Farley, D. T., & Schlegel, K. (1997). Type-1 echoes from the mid-latitude E-region ionosphere. Annales Geophysicae, 15(7), 908-917.