Normal Development: 4 Months Old: References

Centers for Disease Control and Prevention. Important milestones: your baby at four months. https://www.cdc.gov/ncbddd/actearly/milestones/milestones-4mo.html. Updated January 21, 2016. Accessed April 11, 2016.

Hagan J, Shaw J, Duncan P, Eds. Bright Futures Pocket Guide, 3rd ed. American Academy of Pediatrics. http://brightfutures.aap.org/pdfs/BF3%20pocket%20guide_final.pdf. 2011. Accessed April 13, 2016.