@article{ZNSL_1987_160_a14,
     author = {A. Yu. Solynin},
     title = {Some extremal problems for pairs of functions without common values},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {159--169},
     year = {1987},
     volume = {160},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1987_160_a14/}
}