@article{AFM_1997_22_1_a7,
     author = {Seppo Hassi and Henk de Snoo},
     title = {One-dimensional graph perturbations of selfadjoint relations},
     journal = {Annales Fennici Mathematici},
     pages = {123--164},
     publisher = {mathdoc},
     volume = {22},
     number = {1},
     year = {1997},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/AFM_1997_22_1_a7/}
}