Diehl, R. High Energy Astrophysics, MPI for Extraterrestrial Physics, Max Planck Society;
Schönfelder, V. High Energy Astrophysics, MPI for Extraterrestrial Physics, Max Planck Society;
Weidenspointner, G., Shrader, C. R., Knödlseder, J., Jean, P., Lonjou, V., Guessoum, N., et al. (2006). The sky distribution of positronium annihilation continuum emission measured with SPI/INTEGRAL. Astronomy & Astrophysics, 450(3), 1013-1021. doi:10.1051/0004-6361:20054046.