European Centre for Disease Prevention and Control ECDC, Rapid increase of a SARS-CoV-2 variant with multiple spike protein mutations observed in the United Kingdom, 2020-12-20, p. 2 ([Internet, 2020-12-23](https://www.ecdc.europa.eu/sites/default/files/documents/SARS-CoV-2-variant-multiple-spike-protein-mutations-United-Kingdom.pdf))