@article{1103901663,
author = {Maartens, R. and Nel, S. D.},
title = {Decomposable differential operators in a cosmological context},
journal = {Comm. Math. Phys.},
volume = {58},
number = {1},
year = {1978},
pages = { 273-283},
language = {en},
url = {http://dml.mathdoc.fr/item/1103901663}
}
Maartens, R.; Nel, S. D. Decomposable differential operators in a cosmological context. Comm. Math. Phys., Tome 58 (1978) no. 1, pp. 273-283. http://gdmltest.u-ga.fr/item/1103901663/