@article{10_4064_fm_115_1_43_55,
     author = {Jouko V\"a\"an\"anen},
     title = {\ensuremath{\Delta}-extension and {Hanf-numbers}},
     journal = {Fundamenta Mathematicae},
     pages = {43--55},
     publisher = {mathdoc},
     volume = {115},
     number = {1},
     year = {1983},
     doi = {10.4064/fm-115-1-43-55},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-115-1-43-55/}
}