Bill Jackson, Oscar Ordaz. A Chvátal-Erdös condition for (1, 1)-factors in digraphs. Discrete Mathematics, 57(1-2):199-201, 1985. [doi]
@article{JacksonO85,
title = {A Chvátal-Erdös condition for (1, 1)-factors in digraphs},
author = {Bill Jackson and Oscar Ordaz},
year = {1985},
doi = {10.1016/0012-365X(85)90169-4},
url = {http://dx.doi.org/10.1016/0012-365X(85)90169-4},
researchr = {https://researchr.org/publication/JacksonO85},
cites = {0},
citedby = {0},
journal = {Discrete Mathematics},
volume = {57},
number = {1-2},
pages = {199-201},
}