@article{ETNA_2015__44__a11,
     author = {Qiu, Yue and van Gijzen, Martin B. and van Wingerden, Jan-Willem and Verhaegen, Michel and Vuik, Cornelis},
     title = {Efficient preconditioners for {PDE-constrained} optimization problem with a multilevel sequentially semiseparable matrix structure},
     journal = {Electronic transactions on numerical analysis},
     pages = {367--400},
     publisher = {mathdoc},
     volume = {44},
     year = {2015},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ETNA_2015__44__a11/}
}