1. R. Alizade, E. Büyükaşık, and Y. Durgun, “Small supplements, weak supplements, and proper classes,” Hacet. J. Math. Stat., 45, No. 3, 449–461 (2016).
2. R. Alizade, “Global dimension of some proper class,” Usp. Mat. Nauk, 1, 181–182 (1985).
3. R. Alizade, Y. M. Demirci, Y. Durgun, and D. Pusat, “The proper class generated by weak supplements,” Comm. Algebra, 42, 56–72 (2014).
4. D. A. Buchsbaum, “A note on homology in categories,” Ann. Math., 69, 66–74 (1959).
5. A. I. Generalov, The 𝜔-Cohigh Purity in Categories of Modules, Plenum, New York (1983).