@article{10_4064_fm_90_2_159_172,
     author = {E. L\'opez-Escobar},
     title = {On an extremely restricted \ensuremath{\omega}-rule},
     journal = {Fundamenta Mathematicae},
     pages = {159--172},
     publisher = {mathdoc},
     volume = {90},
     number = {2},
     year = {1975},
     doi = {10.4064/fm-90-2-159-172},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-90-2-159-172/}
}