1. Dragana S. Cvetković-Ilić, Marko Kostadinov, Invertibility of linear combinations in , Linear and Multilinear Algebra, 66 (11) (2018), 2139-2150.
2. Dragana S. Cvetković-Ilić, Marko Kostadinov, Consistency in invertibility and Fredholmness of operator matrices, Journal of Spectral Theory, 9 (2019), 635–649.
1.Marko Kostadinov, A note on operators consistent in inveritiblity, Facta Universitatis, Series: Mathematics and Informatics, 34(3) (2019), 429–438.