Retrieved 5 June 2013. ↑ http://www.who.int/mediacentre/factsheets/fs363/en/ ↑ http://www.who.int/mediacentre/factsheets/fs363/en/ ↑ https://www.nih.gov/news-events/news-releases/nih-study-reveals-factors-influence-premature-infant-survival-disability ↑ Glass, H. C.; Costarino, A. T.; Stayer, S. A.; Brett, C; Cladis, F; Davis, P. J. (2015).