@article{10_4064_ap81_3_5,
     author = {J. Chabrowski and E. Tonkes},
     title = {On elliptic systems pertaining
 to the {Schr\"odinger} equation},
     journal = {Annales Polonici Mathematici},
     pages = {273--294},
     year = {2003},
     volume = {81},
     number = {3},
     doi = {10.4064/ap81-3-5},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap81-3-5/}
}