@article{10_14708_cm_v24i2_6096,
     author = {R. Gajewski},
     title = {Some theorems concerning approximation by double orthogonal series},
     journal = {Commentationes Mathematicae},
     pages = { 245--255},
     publisher = {mathdoc},
     volume = {24},
     number = {2},
     year = {1984},
     doi = {10.14708/cm.v24i2.6096},
     language = {pl},
     url = {http://geodesic.mathdoc.fr/articles/10.14708/cm.v24i2.6096/}
}