https://www.censis.it/sites/default/files/downloads/La%20societaitaliana_2021.pdf
https://www.eurofound.europa.eu/sites/default/files/ef_publication/field_ef_document/ef18036en.pdf
http://www.pewforum.org/2018/05/29/being-christian-in-western-europe/
http://hmics.org/sites/default/files/publications/HMICS20170621PUB.pdf