@article{10_1017_S0017089509005060,
     author = {EL-GEBEILY, MOHAMED and O'REGAN, DONAL},
     title = {A {CHARACTERIZATION} {OF} {SELF-ADJOINT} {OPERATORS} {DETERMINED} {BY} {THE} {WEAK} {FORMULATION} {OF} {SECOND-ORDER} {SINGULAR} {DIFFERENTIAL} {EXPRESSIONS}},
     journal = {Glasgow mathematical journal},
     pages = {385--404},
     year = {2009},
     volume = {51},
     number = {2},
     doi = {10.1017/S0017089509005060},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089509005060/}
}