@article{ARM_2011__47_1_a3,
     author = {Van Dung, Nguyen},
     title = {$\pi $-mappings in $ls${-Ponomarev-systems}},
     journal = {Archivum mathematicum},
     pages = {35--49},
     publisher = {mathdoc},
     volume = {47},
     number = {1},
     year = {2011},
     mrnumber = {2813545},
     zbl = {1240.54101},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ARM_2011__47_1_a3/}
}