1. United States vital statistics and the measurement of gestational age;Martin;Paediatric and Perinatal Epidemiology,2007
2. Centers for Disease Control and Prevention Guide to Completing the Facility Worksheets for the Certificate of Live Birth and Report of Fetal Death 2003 http://www.cdc.gov/nchs/data/dvs/guidetocompletefacilitywks.pdf
3. Centers for Disease Control and Prevention Birth Edit Specifications for the 2003 Proposed Revision of the U.S. Standard Certificate of Birth 2003 http://www.cdc.gov/nchs/data/dvs/birth_edit_specifications.pdf
4. Comparison of pregnancy dating by last menstrual period, ultrasound scanning, and their combination;Savitz;American Journal of Obstetrics and Gynecology,2002
5. Assessing number-specific error in the recall of onset of last menstrual period;Waller;Paediatric and Perinatal Epidemiology,2000