Friedery R. Hardening borders during the pandemic in the European Union: The Shape of the Schengen Borders Code and the EU Digital COVID Certificate. QRP - AWR Bulletin [Internet]. 2022 Sep. 20 [cited 2024 Nov. 23];61(1):71-84. Available from: https://ejournals.bibliothek.thws.de/qrp/article/view/29