
http://www.reuters.com/article/us-britain-eu-verhofstadt-idUSKBN19V0WP

https://blogs.lse.ac.uk/europpblog/2023/06/19/is-differentiated-cooperation-the-way-forward-for-eu-foreign-policy/

http://blogs.sussex.ac.uk/uktpo/files/2017/11/Briefing-Paper-11.pdf