The first determination of the viscosity parameter in the circumstellar disk of a Be star - Carciofi, Alex Cavalieri; Bjorkman, Jon E; Otero, Sebastián A; Okazaki, Atsuo T; Stefl, Stanislav; Rivinus, Thomas; Baade, Dietrich; Haubois, Xavier (The Astrophysical Journal Letters, 2012)