Volis, S
Ormanbekova, D
Yermekbayev, K
Abugalieva, S
Turuspekov, Y
Shulgina, I
Article History
Received: 8 July 2015
Revised: 9 December 2015
Accepted: 18 December 2015
First Online: 3 February 2016
Competing interests
: The authors declare no conflict of interest.