@article{MAN_1991__291_1_164870,
     author = {Stephan Herfurtner},
     title = {Elliptic surfaces with four singular fibres.},
     journal = {Mathematische Annalen},
     pages = {319--342},
     publisher = {mathdoc},
     volume = {291},
     number = {1},
     year = {1991},
     zbl = {0762.14018},
     url = {http://geodesic.mathdoc.fr/item/MAN_1991__291_1_164870/}
}