Gaia Data Release 2. The celestial reference frame (Gaia-CRF2)DOI: info:10.1051/0004-6361/201832916v. 616A14
Gaia Collaboration, Mignard, F., Klioner, S. A., Lindegren, L., Hernández, J., Bastian, U., Bombrun, A., Hobbs, D., Lammers, U., Michalik, D., Ramos-Lerate, M., Biermann, M., Fernández-Hernández, J., Geyer, R., Hilger, T., Siddiqui, H. I., Steidelmüller, H., Babusiaux, C., Barache, C., Lambert, S., Andrei, A. H., Bourda, G., Charlot, P., Brown, A. G. A., Vallenari, A. et al. 2018. "Gaia Data Release 2. The celestial reference frame (Gaia-CRF2)." Astronomy and Astrophysics, 616 A14. https://doi.org/10.1051/0004-6361/201832916.