@article{1103859333,
author = {Hawking, S. W.},
title = {A variational principle for black holes},
journal = {Comm. Math. Phys.},
volume = {29},
number = {1},
year = {1973},
pages = { 323-334},
language = {en},
url = {http://dml.mathdoc.fr/item/1103859333}
}
Hawking, S. W. A variational principle for black holes. Comm. Math. Phys., Tome 29 (1973) no. 1, pp. 323-334. http://gdmltest.u-ga.fr/item/1103859333/