Parvinen, I
Heinävaara, S
Anttila, A
Helenius, H
Klemi, P
Pylkkänen, L
Article History
Received: 9 July 2014
Revised: 22 October 2014
Accepted: 1 December 2014
First Online: 17 February 2015
Competing interests
: The authors declare no conflict of interest.