@article{10_4064_ap_39_1_117_130,
     author = {Ewa Ligocka},
     title = {How to prove {Fefferman's} theorem without use of differential geometry},
     journal = {Annales Polonici Mathematici},
     pages = {117--130},
     publisher = {mathdoc},
     volume = {39},
     number = {1},
     year = {1981},
     doi = {10.4064/ap-39-1-117-130},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-39-1-117-130/}
}