1. Average fetal length and weight chart. http://www.babycentre.co.uk/a1004000/average-fetal-length-and-weight-chart.
2. Number of neurons in fetus. http://www.hhmi.org/biointeractive/development-human-embryonic-brain.
3. Child development in 3rd trimester. http://mom.me/pregnancy/12467-pregnancy-brain-and-child-development-third-trimester/.
4. Environmental effects on prenatal development;Dalby;J Pediatr Psychol,1978
5. Insights into early fetal development;Becher,2004