@article{10_4153_CJM_1993_047_1,
     author = {Liu, Linqi},
     title = {Propagation {Of} {Singularities} for {Semilinear} {Hyperbolic} {Equations}},
     journal = {Canadian journal of mathematics},
     pages = {835--846},
     year = {1993},
     volume = {45},
     number = {4},
     doi = {10.4153/CJM-1993-047-1},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1993-047-1/}
}