Regarding the tool:
there are no up to date publications that describe ors in the state it is today.
There are some publications that do a general overview from 2007 and 2008:
https://www.researchgate.net/profile/Alexander-Zipf/publication/228679185_A_Web_Accessibility_Analysis_Service_based_on_the_OpenLS_Route_Service/links/02e7e517aba95b38d6000000/A-Web-Accessibility-Analysis-Service-based-on-the-OpenLS-Route-Service.pdf
or
Otherwise you could just cite our website:
https://openrouteservice.org/
Or directly the repository:
Best regards