@article{RM_2007_62_1_a1,
     author = {V. G. Kanovei and V. A. Lyubetskii},
     title = {Problems in set-theoretic nonstandard analysis},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {45--111},
     publisher = {mathdoc},
     volume = {62},
     number = {1},
     year = {2007},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RM_2007_62_1_a1/}
}