Embassy of the Free Mind (English Wikipedia)

"Joost R. Ritman founder of the Ritman Library in Amsterdam". ritmanlibrary.com. Archived from the original on 2018-10-20. Retrieved 2019-02-27.
"ANBI". ritmanlibrary.com. Archived from the original on 2019-02-13. Retrieved 2019-02-27.
"The Ritman Library » Collection Profile". ritmanlibrary.com. Archived from the original on 2019-02-13. Retrieved 2019-02-27.

theguardian.com

"Dan Brown opent Ambassade van de Vrije Geest in Amsterdam". Nieuw Wij. 22 October 2017. Archived from the original on 13 February 2019. Retrieved 27 February 2019.
"Joost R. Ritman founder of the Ritman Library in Amsterdam". ritmanlibrary.com. Archived from the original on 2018-10-20. Retrieved 2019-02-27.
"ANBI". ritmanlibrary.com. Archived from the original on 2019-02-13. Retrieved 2019-02-27.
"The Ritman Library » Collection Profile". ritmanlibrary.com. Archived from the original on 2019-02-13. Retrieved 2019-02-27.