Ditchev A. SOME PROPERTIES OF AN ALGEBRA OF ALL SETS OF NATURALS E-REDUCIBLE TO A FIXED SET. Ann. Sofia Univ. Fac. Math. and Inf. [Internet]. 2013 Dec. 12 [cited 2024 Nov. 24];101:81-93. Available from: https://ftl5.uni-sofia.bg./index.php/fmi/article/view/231