@article{UZERU_2014_1_a1,
     author = {Yu. R. Akopian and R. Z. Hovhannisyan},
     title = {On the two-level preconditioning in least squares method},
     journal = {Proceedings of the Yerevan State University. Physical and mathematical sciences},
     pages = {7--15},
     publisher = {mathdoc},
     number = {1},
     year = {2014},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/UZERU_2014_1_a1/}
}