How to we reference FreeOpcUa in a paper?

[bserra]

Hi, I am using opcua-asyncio on a raspberry to control and monitor all of our test bench at work and am in the process of publishing a paper on it. Since the OPC server is one very important element, I would like to quote the project but could not find proper reference to this project that I could actually insert in the paper. Anyone has a link of the proper reference?