@article{MZ_1978__158_172622,
     author = {Horst Behncke and Heinz Focke},
     title = {Deficiency {Indices} of {Singular} {Schr\"odinger} {Operators.}},
     journal = {Mathematische Zeitschrift},
     pages = {87--98},
     year = {1978},
     volume = {158},
     zbl = {0353.35033},
     url = {http://geodesic.mathdoc.fr/item/MZ_1978__158_172622/}
}