2 citations to https://www.mathnet.ru/rus/dan21414

1. N. A. Izobov, A. V. Il'in, “On the Baire Classification of Positive Characteristic Exponents in the Perron Effect of Change of Their Values”, Diff Equat, 54:11 (2018), 1409  
2. S. K. Korovin, N. A. Izobov, “Multidimensional Perron sign change effect for all characteristic exponents of differential systems”, Dokl. Math., 85:3 (2012), 315