@article{MT_1994_27_a1,
     author = {A. A. Ageev},
     title = {Complexity of the network problem of a median on planar lattices},
     journal = {Matemati\v{c}eskie trudy},
     pages = {6--13},
     publisher = {mathdoc},
     volume = {27},
     year = {1994},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MT_1994_27_a1/}
}