@article{DE_1990_26_10_a1,
     author = {V. I. Borzdyko},
     title = {A topological method for proving the existence of positive periodic solutions for functional-differential equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1671--1678},
     publisher = {mathdoc},
     volume = {26},
     number = {10},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1990_26_10_a1/}
}