@article{MAN_1991__291_1_164853,
     author = {Massimiliano Pontecorvo},
     title = {Algebraic dimension of twistor spaces and scalar curvature of anti-self-dual metrics.},
     journal = {Mathematische Annalen},
     pages = {113--122},
     publisher = {mathdoc},
     volume = {291},
     number = {1},
     year = {1991},
     zbl = {0747.32021},
     url = {http://geodesic.mathdoc.fr/item/MAN_1991__291_1_164853/}
}