A.~Lunin, T.N.~Khabiboulline, N.~Solyak, and V.P.~Yakovlev,
   "Development of a Button BPM for the LCLS-II project",
   in Proc. 3rd International Beam Instrumentation Conference, Monterey, CA, USA, paper TUPF18, pp. 361–364,
    ISBN: 978-3-95450-141-0,
    \url{http://jacow.org/IBIC2014/papers/tupf18.pdf},
    2014.