@article{GDZPPN002269856, title = {Riemann spaces conformal to Einstein spaces}, journal = {Mathematische Annalen}, volume = {92}, year = {1924}, pages = {269-278}, zbl = {50.0504.01}, url = {http://dml.mathdoc.fr/item/GDZPPN002269856} }
Brinkmann, H.W. Riemann spaces conformal to Einstein spaces. Mathematische Annalen, Tome 92 (1924) pp. 269-278. http://gdmltest.u-ga.fr/item/GDZPPN002269856/