Мустафа, М., and К. Ш. Абешев. “ On the Existence of Families of Sets Without Minimal Computable Numberings in the Ershov Hierarchy”. Journal of Mathematics, Mechanics and Computer Science 78, no. 3 (September 29, 2013): 83–86. Accessed July 22, 2024. https://bm.kaznu.kz/index.php/kaznu/article/view/109.