@article{05909730, title = {Global eikonal condition for Lorentzian distance function in noncommutative geometry.}, journal = {SIGMA. Symmetry, Integrability and Geometry: Methods and Applications [electronic only]}, volume = {6}, year = {2010}, doi = {10.3842/SIGMA.2010.064}, zbl = {1217.58006}, language = {en}, url = {http://dml.mathdoc.fr/item/05909730} }
Franco, Nicolas. Global eikonal condition for Lorentzian distance function in noncommutative geometry.. SIGMA. Symmetry, Integrability and Geometry: Methods and Applications [electronic only], Tome 6 (2010) . doi : 10.3842/SIGMA.2010.064. http://gdmltest.u-ga.fr/item/05909730/