@article{EJDE_1998__1998__a2,
     author = {Carlson,  Robert},
     title = {Adjoint and self-adjoint differential operators on graphs},
     journal = {Electronic journal of differential equations},
     year = {1998},
     volume = {1998},
     zbl = {0888.34055},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_1998__1998__a2/}
}