@article{M2AN_2006__40_1_49_0,
     author = {Flad, Heinz-J\"urgen and Hackbusch, Wolfgang and Schneider, Reinhold},
     title = {Best $N$-term approximation in electronic structure calculations {I.} {One-electron} reduced density matrix},
     journal = {ESAIM: Mod\'elisation math\'ematique et analyse num\'erique},
     pages = {49--61},
     publisher = {EDP-Sciences},
     volume = {40},
     number = {1},
     year = {2006},
     doi = {10.1051/m2an:2006007},
     mrnumber = {2223504},
     zbl = {1100.81050},
     language = {en},
     url = {http://archive.numdam.org/articles/10.1051/m2an:2006007/}
}