@article{PORMA_1999__56_2_48455,
     author = {Joshi, M.S.},
     title = {Geometric proofs of composition theorems for generalized {Fourier} integral operators.},
     journal = {Portugaliae mathematica},
     pages = {129--154},
     publisher = {mathdoc},
     volume = {56},
     number = {2},
     year = {1999},
     zbl = {0939.35203},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1999__56_2_48455/}
}