Keller, H. U. Department Planets and Comets, Max Planck Institute for Solar System Research, Max Planck Society; MPI for Aeronomy, Max Planck Institute for Solar System Research, Max Planck Society;
Huebner, W. F., & Keller, H. U. (2005). Apparent inconsistencies in the formation of cometary matter. IAU Symposia, 13(A9), 473-475.