@article{ELA_2010__20__a15,
     author = {Zhao, Lin-Lin and Chen, Guo-Linag and Liu, Qing-Bin},
     title = {Least squares {(P,Q)-orthogonal} symmetric solutions of the matrix equation and its optimal approximation},
     journal = {The electronic journal of linear algebra},
     pages = {537--551},
     publisher = {mathdoc},
     volume = {20},
     year = {2010},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ELA_2010__20__a15/}
}