@article{TMF_2018_195_2_a7,
     author = {M. Fathi and M. Mohseni},
     title = {Congruence convergence in pp-wave space--time},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {269--287},
     publisher = {mathdoc},
     volume = {195},
     number = {2},
     year = {2018},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_2018_195_2_a7/}
}