@article{GDZPPN00229205X,
title = {A Reduction-Principle for Infinite Formulas.},
journal = {Mathematische Annalen},
volume = {152},
year = {1963},
pages = {296-303},
zbl = {0114.24504},
url = {http://dml.mathdoc.fr/item/GDZPPN00229205X}
}
ENGELER, E. A Reduction-Principle for Infinite Formulas.. Mathematische Annalen, Tome 152 (1963) pp. 296-303. http://gdmltest.u-ga.fr/item/GDZPPN00229205X/