@article{VTAMU_2020_25_130_a1,
     author = {M. J. Alves and S. M. Labovski},
     title = {On the spectral properties and positivity of solutions of a periodic boundary value problem for a second-order functional differential equation},
     journal = {Vestnik rossijskih universitetov. Matematika},
     pages = {123--130},
     publisher = {mathdoc},
     volume = {25},
     number = {130},
     year = {2020},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VTAMU_2020_25_130_a1/}
}