@article{10_4064_cm_53_2_157_168,
     author = {Krzysztof Pra\.zmowski},
     title = {Groups of squares and half-equivalences in geometry},
     journal = {Colloquium Mathematicum},
     pages = {157--168},
     publisher = {mathdoc},
     volume = {53},
     number = {2},
     year = {1987},
     doi = {10.4064/cm-53-2-157-168},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-53-2-157-168/}
}