@article{1104253397,
author = {Nelson, J. E. and Regge, T.},
title = {Invariants of $2+1$ gravity},
journal = {Comm. Math. Phys.},
volume = {151},
number = {1},
year = {1993},
pages = { 561-568},
language = {en},
url = {http://dml.mathdoc.fr/item/1104253397}
}
Nelson, J. E.; Regge, T. Invariants of $2+1$ gravity. Comm. Math. Phys., Tome 151 (1993) no. 1, pp. 561-568. http://gdmltest.u-ga.fr/item/1104253397/