@article{10_4064_ap_56_2_163_178,
     author = {Salvatore Marano},
     title = {Classical solutions of hyperbolic partial differential equations with implicit mixed derivative},
     journal = {Annales Polonici Mathematici},
     pages = {163--178},
     publisher = {mathdoc},
     volume = {56},
     number = {2},
     year = {1991},
     doi = {10.4064/ap-56-2-163-178},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-56-2-163-178/}
}