@article{MABA_1998_12_3-4_a1,
     author = {A. Canoglu and D. P. Allahverdiev},
     title = {Extensions of a {Symmetric} {Second-Order} {Differential} {Operator}},
     journal = {Mathematica balkanica},
     pages = {271},
     publisher = {mathdoc},
     volume = {12},
     number = {3-4},
     year = {1998},
     url = {http://geodesic.mathdoc.fr/item/MABA_1998_12_3-4_a1/}
}