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Crabtree JE, Wyatt JI, Sobala GM, Miller G, Tompkins DS, Primrose JN, Morgan AG.Crabtree JE, et al. Among authors: primrose jn.Gut. 1993 Oct;34(10):1339-43. doi: 10.1136/gut.34.10.1339.Gut. 1993.PMID: 8244098Free PMC article.