@article{MAN_1991__289_4_164790,
     author = {Andrew Swann},
     title = {Hyper {K\"ahler} and quaternionic {K\"ahler} geometry.},
     journal = {Mathematische Annalen},
     pages = {421--450},
     publisher = {mathdoc},
     volume = {289},
     number = {4},
     year = {1991},
     zbl = {0711.53051},
     url = {http://geodesic.mathdoc.fr/item/MAN_1991__289_4_164790/}
}