http://economics.mit.edu/files/12979
https://www.socialeurope.eu/ryanair-on-the-side-of-europes-citizens
https://www.socialeurope.eu/social-dialogue-in-central-and-eastern-europe
https://www.vatican.va/content/leo-xiii/en/encyclicals/documents/hf_l-xiii_enc_15051891_rerum-novarum.html