BMJ 6 ( j j j j éäàéäàéäàéäàj j j j °°°°°°°°°°°°éäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàéäàÿÿÿÿÿÿÿÿÿÿÿÿj j j j éäàéäàéäàéäàéäàéäàéäàéäàj j j j