Halbgebauer, Steffen
Nagl, Magdalena
Klafki, Hans
Haußmann, Ute
Steinacker, Petra
Oeckl, Patrick
Kassubek, Jan
Pinkhardt, Elmar
Ludolph, Albert C.
Soininen, Hilkka
Herukka, Sanna-Kaisa
Wiltfang, Jens
Otto, Markus
Article History
Received: 15 November 2015
Accepted: 28 April 2016
First Online: 17 May 2016
Competing interests
: The authors declare no competing financial interests.