Mikko Tuomi, Guillem Anglada-Escudé, Enrico Gerlach, Hugh R. A. Jones, Ansgar Reiners, Eugenio J. Rivera, Steven S. Vogt & R. Paul Butler: Habitable-zone super-Earth candidate in a six-planet system around the K2.5V star HD 40307.Astronomy & Astrophysics, November 8, 2012 PDF