Features and problems of implementation of trilingual system in the secondary school in KazakhstanUlan Tlemissov, Arafat Mamyrbekov, Aibar Kadyrov, Indira Oralkanova, Syrym Yessenov and Zhansaya TlemissovaE3S Web Conf., 159 (2020) 09005DOI: https://doi.org/10.1051/e3sconf/202015909005