Robert W. Robinson. Counting strong digraphs. Journal of Graph Theory, 1(2):189-190, 1977. [doi]
@article{Robinson77,
title = {Counting strong digraphs},
author = {Robert W. Robinson},
year = {1977},
doi = {10.1002/jgt.3190010215},
url = {http://dx.doi.org/10.1002/jgt.3190010215},
researchr = {https://researchr.org/publication/Robinson77},
cites = {0},
citedby = {0},
journal = {Journal of Graph Theory},
volume = {1},
number = {2},
pages = {189-190},
}