@article{MABA_1998_12_3-4_a0,
     author = {N. Bozhinov and E. M. Elabd},
     title = {Joint {Root} {Function} {Expansion} of the {Nonlocal} {Partial} {Integro-Differential} {Operators} of {First} and {Second} {Order}},
     journal = {Mathematica balkanica},
     pages = {253},
     publisher = {mathdoc},
     volume = {12},
     number = {3-4},
     year = {1998},
     url = {http://geodesic.mathdoc.fr/item/MABA_1998_12_3-4_a0/}
}