@article{ZNSL_1991_187_a5,
     author = {A. A. Kapaev},
     title = {Weaknonlinear solutions of the $\mathbb{P}_1^2$ equation},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {88--109},
     publisher = {mathdoc},
     volume = {187},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1991_187_a5/}
}