Widdel, H. U. MPI for Aeronomy, Max Planck Institute for Solar System Research, Max Planck Society;
Widdel, H. U. (1996). Foil chaff cloud method. In W. Dieminger, G. K. Hartmann, & R. Leitinger (Eds.), The Upper Atmosphere: Data Analysis and Interpretation (pp. 227-241). Berlin: Springer.