@article{EUG_1988__20_a13,
     author = {E. C. Zachmanoglou},
     title = {Solutions which are flat or {Singular} on {Totally} {Characteristic} {Manifolds} of first order {Partial} {Differential} {Equations} },
     journal = {E\ensuremath{\upsilon}\ensuremath{\kappa}\ensuremath{\lambda}\ensuremath{\varepsilon}\ensuremath{\acute\iota}\ensuremath{\delta}\ensuremath{\eta}\ensuremath{\varsigma} \ensuremath{\Gamma}
},
     pages = {149-158},
     publisher = {mathdoc},
     volume = {20},
     year = {1988},
     language = {gr},
     url = {http://geodesic.mathdoc.fr/item/EUG_1988__20_a13/}
}