Voir la notice de l'article provenant de la source European Digital Mathematics Library
@article{MS_1964__107_2_a1, author = {{\CYRI}.{\CYRT}. {\CYRK}{\cyri}{\cyrg}{\cyru}{\cyrr}{\cyra}{\cyrd}{\cyrz}{\cyre}}, title = {{\CYRO} {\cyrk}{\cyro}{\cyrl}{\cyre}{\cyrb}{\cyrl}{\cyre}{\cyrm}{\cyro}{\cyrs}{\cyrt}{\cyri} {\cyrr}{\cyre}{\cyrsh}{\cyre}{\cyrn}{\cyri}{\cyrishrt} {\cyru}{\cyrr}{\cyra}{\cyrv}{\cyrn}{\cyre}{\cyrn}{\cyri}{\cyrya} $d^m u/dt^m +a(t)|u|^n \text{sign}\,u = 0$}, journal = {Matemati\v{c}eskij sbornik}, pages = {172--187}, publisher = {mathdoc}, volume = {107}, number = {2}, year = {1964}, zbl = {0135.14302}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/MS_1964__107_2_a1/} }
И.Т. Кигурадзе. О колеблемости решений уравнения $d^m u/dt^m +a(t)|u|^n \text{sign}\,u = 0$. Matematičeskij sbornik, Tome 107 (1964) no. 2, pp. 172-187. http://geodesic.mathdoc.fr/item/MS_1964__107_2_a1/