@article{AMLG_1969__12_137820,
     author = {H. Leblanc and R.K. Meyer},
     title = {Open formulas and the empty domain.},
     journal = {Archiv f\"ur mathematische Logik und Grundlagenforschung},
     pages = {78--84},
     publisher = {mathdoc},
     volume = {12},
     year = {1969},
     zbl = {0181.29801},
     url = {http://geodesic.mathdoc.fr/item/AMLG_1969__12_137820/}
}