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Birch JM, Marsden HB, Jones PH, Pearson D, Blair V.Birch JM, et al. Among authors: marsden hb.Br Med J (Clin Res Ed). 1988 May 14;296(6633):1372-6. doi: 10.1136/bmj.296.6633.1372.Br Med J (Clin Res Ed). 1988.PMID: 2840171Free PMC article.