Funding for this research was provided by:
Tomsk State University (N/A)
Received: 23 October 2018
Accepted: 11 March 2019
First Online: 14 March 2019
Ethics approval and consent to participate
: The study was approved by the local Committee on Bioethics of the School of Public Health of al-Farabi Kazakh National University. Each subject in this study signed an informed consent to participate.
: Not applicable.
: The authors declare that they have no competing interests.
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