@article{IM_1990__99_1_143763,
     author = {D.L. Ulmer},
     title = {On universal elliptic curves over {Igusa} curves.},
     journal = {Inventiones mathematicae},
     pages = {377--392},
     publisher = {mathdoc},
     volume = {99},
     number = {1},
     year = {1990},
     zbl = {0705.14024},
     url = {http://geodesic.mathdoc.fr/item/IM_1990__99_1_143763/}
}