@article{10_4064_fm_92_2_141_147,
     author = {Ping-Fun Lam},
     title = {Discrete and continuous flows of characteristic $O^\ensuremath{\pm}$},
     journal = {Fundamenta Mathematicae},
     pages = {141--147},
     publisher = {mathdoc},
     volume = {92},
     number = {2},
     year = {1976},
     doi = {10.4064/fm-92-2-141-147},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-92-2-141-147/}
}