We select the letters for these pages from the rapid responses posted on bmj.com favouring those received within five days of publication of the article to which they refer.Letters are thus an early selection of rapid responses on a particular topic.Readers should consult the website for the full list of responses and any authors' replies, which usually arrive after our selection.
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Ford et al. (2007) studied this question.
Synapse has enriched one closely related paper. Consider it for comparative context: