G. Cherlin, Péter Komjáth. There is no universal countable pentagon-free graph. Journal of Graph Theory, 18(4):337-341, 1994. [doi]
@article{CherlinK94,
title = {There is no universal countable pentagon-free graph},
author = {G. Cherlin and Péter Komjáth},
year = {1994},
doi = {10.1002/jgt.3190180405},
url = {http://dx.doi.org/10.1002/jgt.3190180405},
researchr = {https://researchr.org/publication/CherlinK94},
cites = {0},
citedby = {0},
journal = {Journal of Graph Theory},
volume = {18},
number = {4},
pages = {337-341},
}