2 citations to https://www.mathnet.ru/rus/dan31599

1. H. G. Ghazaryan, “On selection of infinitely differentiable solutions of a class of partially hypoelliptic equations”, Eurasian Math. J., 3:1 (2012), 41–62      
2. А. Д. Брюно, “Автомодельные решения и степенная геометрия”, УМН, 55:1(331) (2000), 3–44            ; A. D. Bruno, “Self-similar solutions and power geometry”, Russian Math. Surveys, 55:1 (2000), 1–42