Foto de stock - 29 September 2021, North Rhine-Westphalia, Duisburg: View of an overhead projector in a lecture hall at the University of Duisburg-Essen. For thousands of students, the new winter semester 2021/2022 at the universities of North Rhine-Westphalia will start on October 1, 2021, with a lot of presence and the ""3Gs"". After three semesters of digital or hybrid teaching under corona conditions, this will be the first time in a long time that many students will see the inside of the university building again. In return, they have to show that they have been vaccinated, have recovered or have been tested. Photo: Rolf Vennenbernd/dpa. - Duisburg/North Rhine-Westphalia/Germany