Tyulemissov, Z. Z., N. Habyl, S. A. Zhaugasheva, G. S. Nurbakova, and G. G. Saidullaeva. “Significance of Confinement in Covariant Quark Model”. International Journal of Mathematics and Physics, vol. 6, no. 1, Dec. 2015, pp. 88-91, https://ijmph.kaznu.kz/index.php/kaznu/article/view/126.