@article{1103859285, author = {Sachs, R. K.}, title = {Spacetime $b$-boundaries}, journal = {Comm. Math. Phys.}, volume = {29}, number = {1}, year = {1973}, pages = { 215-220}, language = {en}, url = {http://dml.mathdoc.fr/item/1103859285} }
Sachs, R. K. Spacetime $b$-boundaries. Comm. Math. Phys., Tome 29 (1973) no. 1, pp. 215-220. http://gdmltest.u-ga.fr/item/1103859285/