@article{AMLG_1978__19_137951,
     author = {Georges Blanc},
     title = {\'Equivalence naturelle et formules logiques en th\'eorie des cat\'egories.},
     journal = {Archiv f\"ur mathematische Logik und Grundlagenforschung},
     pages = {131--138},
     publisher = {mathdoc},
     volume = {19},
     year = {1978},
     zbl = {0407.03035},
     url = {http://geodesic.mathdoc.fr/item/AMLG_1978__19_137951/}
}