Gizatulla Imashev, Nurgul S. Zhazylbaeva, Zhadyra Salykbayeva, Zhadyra G. Shimakova, Aigul Kh. Yerekeshova, Baktygul K. Suleimenova, Shara Zh. Syrbayeva
INT ELECT J MATH ED, Volume 11, Issue 7, 2016, 2099-2111