@article{VMUMM_1989_5_a21,
     author = {O. V. Popov},
     title = {On quadratic residues and nonresidues in a sequence of square-free numbers},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {81--83},
     publisher = {mathdoc},
     number = {5},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_1989_5_a21/}
}