@article{AM2_1982__25_136965,
     author = {J.A. Lester},
     title = {Transformations of {Robertson-Walker} spacetimes preserving separation zero.},
     journal = {Aequationes mathematicae},
     pages = {216--232},
     publisher = {mathdoc},
     volume = {25},
     year = {1982},
     zbl = {0538.53062},
     url = {http://geodesic.mathdoc.fr/item/AM2_1982__25_136965/}
}