Current State of Avogadro 28Si sphere S8. - R. Arnold Nicolaus; Guido Bartl; Horst Bettin; Michael Borys; Martin Firlus; Ingo Busch; Andre Felgner; Rolf Kruger-Sehm; Michael Krumrey; Michael Krystek; Ulrich Kuetgens (IEEE Trans. Instrum. Meas., 2013)