Baimolda, D., T. Cechak, and S. Shyngysova. “DETERMINATION OF ASH CONTENT IN COAL BY X-RAY FLUORESCENCE ANALYSIS”. Bulletin of Abai KazNPU. Series of Physical and Mathematical Sciences, vol. 73, no. 1, Mar. 2021, pp. 82-84, doi:10.51889/2021-1.1728-7901.11.