@article{1103842577,
author = {Walker, Martin and Penrose, Roger},
title = {On quadratic first integrals of the geodesic equations for type $\{22\}$ spacetimes},
journal = {Comm. Math. Phys.},
volume = {16},
number = {1},
year = {1970},
pages = { 265-274},
language = {en},
url = {http://dml.mathdoc.fr/item/1103842577}
}
Walker, Martin; Penrose, Roger. On quadratic first integrals of the geodesic equations for type $\{22\}$ spacetimes. Comm. Math. Phys., Tome 16 (1970) no. 1, pp. 265-274. http://gdmltest.u-ga.fr/item/1103842577/