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2. Comparison of chorionic villus sampling and amniocentesis for fetal karyotyping at 10–13 weeks' gestation;Nicolaides;Lancet,1994
3. Gamma nail versus sliding hip screw for extracapsular hip fractures;Parker,1999
4. Variations in operative delivery rates;Lomas,1989
5. Quality of life assessment and survival data;Billingham,1998