2Valori RM. Natural history of disease[A]. In: McGovern DPB, Summerskill WSM, Valori RM, et al. Key topics in evidence-based medicine[M]. Oxford: BIOS Scientific Publishers Limited, 2001.1-3.
3Sacker DL, Straus SE, Richardson WS, et al. Evidence-based medicine: how to practise and teach EBM. 2nd ed[M] .London:Churchill Livingstone, 2000.67-168.