@article{AMLG_1974__16_137891,
     author = {Hidehisa Sakai},
     title = {On necessary but not-sufficient conditions.},
     journal = {Archiv f\"ur mathematische Logik und Grundlagenforschung},
     pages = {143--146},
     publisher = {mathdoc},
     volume = {16},
     year = {1974},
     zbl = {0291.02024},
     url = {http://geodesic.mathdoc.fr/item/AMLG_1974__16_137891/}
}