@article{EJDE_2003__2003__a146,
     author = {Grammatikopoulos, Myron.K. and Hristov, Tzvetan D. and Popivanov, Nedyu I.},
     title = {Singular solutions to {Protter's} problem for the {3-D} wave equation involving lower order terms},
     journal = {Electronic Journal of Differential Equations},
     publisher = {mathdoc},
     volume = {2003},
     year = {2003},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2003__2003__a146/}
}