Thomas A, Danon L, Christensen H, Northstone K, Smith D, Nixon E, Trickey A, Hemani G, Sauchelli S, Finn A, Timpson N, Brooks-Pollock E. Limits of lockdown: characterising essential contacts during physical distancing. Wellcome Open Res. 2021 May;6:116. doi: 10.12688/wellcomeopenres.16785.1
Dreyer NA, Loughlin JE, Rothman KJ. Epidemiologic safety surveillance of cellular telephones in the US. Radiat Prot Dosimetry. 1999 Jun;83(1):159-63.