@article{MS2_1981__49_166768,
     author = {Chih-Han Sah},
     title = {Scissors congruences, {I.} {The} {Gauss-Bonnet} map.},
     journal = {Mathematica Scandinavica},
     pages = {181--210},
     publisher = {mathdoc},
     volume = {49},
     year = {1981},
     zbl = {0496.52003},
     url = {http://geodesic.mathdoc.fr/item/MS2_1981__49_166768/}
}