@article{MZ_1973__132_171931,
     author = {G. Ananda Swarup},
     title = {Projective {Planes} in {Irreducible} {3-Manifolds.}},
     journal = {Mathematische Zeitschrift},
     pages = {305--318},
     publisher = {mathdoc},
     volume = {132},
     year = {1973},
     zbl = {0249.57003},
     url = {http://geodesic.mathdoc.fr/item/MZ_1973__132_171931/}
}