Ojanperä, Ilkka
Kriikku, Pirkko
Vuori, Erkki
Article History
Received: 31 December 2015
Accepted: 7 March 2016
First Online: 17 March 2016
Compliance with ethical standards
: The study was conducted in accordance with all applicable local and international laws and regulations. For this type of study, formal consent is not required.
: The authors declare that they have no conflict of interest.