Nulle, Anda
Tjurina, Uljana
Erts, Renars
Vetra, Anita
Article History
Received: 5 July 2016
Revised: 17 August 2017
Accepted: 17 August 2017
First Online: 6 December 2017
Compliance with ethical standards
:
: The authors declare that they have no competing interests.