1. Arnold, F., Kissel, J., Krankowsky, D., Wieder, H., and Zahringer, J. 1971, J. Atmosph. Terr. Phys., 33, 1963
2. Arnold, F., Joos, W., Hettmannsperger, E., Krankowsky, D., Marien, K.H., and Grochulska, J. 1974, Yearly Report of the Max-Planck-Institute for Nuclear Physics, Heidelberg, Germany
3. Arnold, F., Böhringer, H., Hettmannsperger, E., Krankowsky, D., Stanisławska, J., and Zettwitz, E. 1975, Yearly Report of the Max-Planck-Institute for Nuclear Physics, Heidelberg, Germany
4. Arnold, F., Böhringer, H., Harke, U., Hettmannsperger, E., Krankowsky, D., Marien, K.H., Stanisławska, J., and Zettwitz, E. 1976, Yearly Report of the Max-Planck-Institute for Nuclear Physics, Heidelberg, Germany
5. Arnold, F., Krankowsky, D., and Marien, K.H. 1977a, Nature, 267, 30