7Murphy C, Russo A. An update on ergonomic issues in sonography[R]. Employee Health and Safety Services, Healthcare Benefit Trust Report,July 2000..1 - 14.
8Bell DM,Shapiro CN,Gooch BF,et al. Hepatitis B Virus in- fection in dentistry[J]. J Public Health Dent, 1993,53 (2) : 170.