Gerhard, Ortwin Optical and Interpretative Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;
Arnaboldi, M., Gerhard, O., Okamura, S., Kashikawa, N., Yasuda, N., & Freeman, K. C. (2007). Multi-slit imaging spectroscopy technique: catalog of intracluster planetary nebulae in the coma cluster. Publications of the Astronomical Society of Japan, 59(2), 419-425.