Poggiali, Erika, et al. “Negative Nasopharyngeal Swabs in COVID-19 Pneumonia: The Experience of an Italian Emergengy Department (Piacenza) During the First Month of the Italian Epidemic”. Acta Biomedica Atenei Parmensis, vol. 91, no. 3, Sept. 2020, p. e2020024, https://doi.org/10.23750/abm.v91i3.9979.