"There is no one who helps you with it": experiences of people with long COVID regarding medical care, therapeutic measures, and barriers in the German healthcare system: results of a qualitative study with four focus groups. - Schmachtenberg T; Königs G; Dragaqina A; Roder S; Müller F; Müllenmeister C; Schröder D; Dopfer-Jablonka A; Vieth K; El-Sayed I (BMC health services research, 2023)