%0 Journal Article
%A Grammatikopoulos,  Myron K.
%A Hristov,  Tzvetan D.
%A Popivanov,  Nedyu I.
%T On the singularities of 3-D Protter's problem for the wave equation
%J Electronic journal of differential equations
%D 2001
%V 2001
%U http://geodesic.mathdoc.fr/item/EJDE_2001__2001__a21/
%G en
%F EJDE_2001__2001__a21