@article{1028997952,
author = {Harary, Frank},
title = {The number of oriented graphs.},
journal = {Michigan Math. J.},
volume = {4},
number = {2},
year = {1957},
pages = { 221-224},
language = {en},
url = {http://dml.mathdoc.fr/item/1028997952}
}
Harary, Frank. The number of oriented graphs.. Michigan Math. J., Tome 4 (1957) no. 2, pp. 221-224. http://gdmltest.u-ga.fr/item/1028997952/