1. Epidemiology of preterm birth and its clinical subtypes;Ananth;J Matern Fetal Neonatal Med,2006
2. Annual summary of vital statistics—2003;Martin;Pediatrics,2005
3. National Center for Health Statistics, 2000. Prepared for the March of Dimes Birth Defects Foundation, 2003. In: Gary Cunningham F, et al, editors. Williams obstetrics. McGraw-Hill Interamericana; 2006. p. 856.
4. Tocolytic treatment for the management of preterm labour: a systematic review;Tan;Singapore Med J,2006
5. Ritodrine in the treatment of preterm labour: a meta-analysis;Li;Indian J Med Res,2005