Magnuson, M.
Schmitt, T.
Strocov, V. N.
Schlappa, J.
Kalabukhov, A. S.
Duda, L.-C.
Article History
Received: 28 July 2014
Accepted: 20 October 2014
First Online: 12 November 2014
Competing interests
: The authors declare no competing financial interests.