Khadzhiivanov, N., and E. Šchepin. “Cohomologies of Countable Unions of Closed Sets With Applications to Cantor Manifolds”. Ann. Sofia Univ. Fac. Math. And Inf., vol. 87, Dec. 1995, pp. 249-55, https://annual.uni-sofia.bg/index.php/fmi/article/view/418.