Komossa, S. Max Planck Institute for Radio Astronomy, Max Planck Society;
Berton, M., Ciroi, S., Congiu, E., Chen, S., Crepaldi, L., Di Mille, F., et al. (2019). Spectroscopic observations of the flaring gamma-ray narrow-line Seyfert 1 PKS 2004-447. The Astronomer's Telegram, 13259, 1.