1. WHO.2018.Preterm birth.http://www.who.int/en/news-room/fact-sheets/detail/preterm-birth.
2. WHO March of Dimes PMNCH Save the Children. 15 million preterm births: Priorities for action based on national regional and global estimates. In:HowsonCP KinneyMV LawnJ eds.Born Too Soon: The Global Action Report on Preterm Birth.2012.
3. Global, regional, and national estimates of levels of preterm birth in 2014: a systematic review and modelling analysis
4. 2019 United Nations Children’s Fund New York NY United Nations Inter‐agency Group for Child Mortality Estimation (UN IGME) ‘Levels & Trends in Child Mortality: Report
5. United Nations.Sustainable Development Goal 3. Ensure healthy lives and promote well‐being for all at all ages.https://www.un.org/sustainabledevelopment/health/.