The study period is end of March to end of April. Masks in the Frankfurt pedestrian zone became obligatory in October [1]. I will amend my summary. [1] https:/

The study period is end of March to end of April. Masks in the Frankfurt pedestrian zone became obligatory in October [1]. I will amend my summary. [1] https://www.msn.com/de-de/nachrichten/panorama/ab-freitag-maskenpflicht-auf-frankfurter-zeil/ar-BB19PkFR https://www.msn.com/de-de/nachrichten/panorama/ab-freitag-ma...