Text and Data Mining valid from 2018-06-26
Received: 6 January 2018
Accepted: 19 June 2018
First Online: 26 June 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: All procedures performed in the present study involving human participants were in accordance with the ethical standards of the Ethical Committee of Tartu University, Estonia (Protocol No. 234/T-5) and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
: Informed consent was obtained from all individual participants included in the study.