@article{10_4064__41_1_153_161,
     author = {Michael Heller and Wies{\l}aw Sasin},
     title = {The closed {Friedman} world model with the initial and final singularities as a non-commutative space},
     journal = {Banach Center Publications},
     pages = {153--161},
     publisher = {mathdoc},
     volume = {41},
     number = {1},
     year = {1997},
     doi = {10.4064/-41-1-153-161},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/-41-1-153-161/}
}