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Urquhart JD, Black RJ, Muirhead MJ, Sharp L, Maxwell M, Eden OB, Jones DA.Urquhart JD, et al. Among authors: muirhead mj.BMJ. 1991 Mar 23;302(6778):687-92. doi: 10.1136/bmj.302.6778.687.BMJ. 1991.PMID: 2021742Free PMC article.