S.~Ackermann, B.~Faatz, and V.~Miltchev,
   "Characterization of the Laser Beam for HHG Seeding",
   in Proc. 3rd International Beam Instrumentation Conference, Monterey, CA, USA, paper TUPF25, pp. 380–384,
    ISBN: 978-3-95450-141-0,
    \url{http://jacow.org/IBIC2014/papers/tupf25.pdf},
    2014.