Real-time monitoring shows substantial excess all-cause mortality during second wave of COVID-19 in Europe, October to December 2020, Nørgaard, Sarah K., Vestergaard Lasse S., Nielsen Jens, Richter Lukas, Schmid Daniela, Bustos Sierra Natalia, Braeye Toon, Athanasiadou Maria, Lytras Theodore, Denissov Gleb, et al. , Eurosurveillance, Feb-01-2022, Volume 26, Issue 2, (2021)