@article{10_4064_fm_44_1_52_60,
     author = {J. {\L}o\'s and R. Suszko},
     title = {On the extending of models {(IV)}},
     journal = {Fundamenta Mathematicae},
     pages = {52--60},
     publisher = {mathdoc},
     volume = {44},
     number = {1},
     year = {1957},
     doi = {10.4064/fm-44-1-52-60},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-44-1-52-60/}
}