1Barvara HB,Beverly GC,Parvati R,et al.Emergency deparunet screening for ectopic pregnancy;a prospective US study[J].Radiology,1994,190:797
2Thoma ME.Early detection of ectopic pregnancy visualizing the presence of a tubal ring with ultrasonography performed by emergeny physicians[J].Am J Emerg Med,2000,18:444
3Gracia Cr,Barnhart KT.Diagnosing ectopic pregnancy;decision analysis comparing six strategies[J].Obstet Gynecol,2001,97:464