Any publication referencing OR-Tools should cite it as follows, updating the version number as appropriate:
OR-Tools v9.5. Laurent Perron and Vincent Furnon. https://developers.google.com/optimization/.
BibTeX:
@software{ortools,
title = {OR-Tools},
version = { v9.5 },
author = {Laurent Perron and Vincent Furnon},
organization = {Google},
url = {https://developers.google.com/optimization/},
date = { 2022-11-25 }
}