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
Britt DM, Cohen LM, Collins FL, Cohen ML. Cigarette smoking and chewing gum: response to a laboratory-induced stressor. Health Psychol. 2001 Sep 1;20(5):361-8.