@article{MAN_1976__224_162901,
     author = {Friedrich Hegenbarth},
     title = {Examples of {Free} {Involutions} on {Manifolds.}},
     journal = {Mathematische Annalen},
     pages = {117--128},
     publisher = {mathdoc},
     volume = {224},
     year = {1976},
     zbl = {0321.57030},
     url = {http://geodesic.mathdoc.fr/item/MAN_1976__224_162901/}
}