Kids Health. https://kidshealth.org/en/parents/week31.html
Diakses pada 9 September 2020Parents. https://www.parents.com/pregnancy/week-by-week/31/
Diakses pada 9 September 2020Baby Center. https://www.babycenter.com/pregnancy/week-by-week/31-weeks-pregnant
Diakses pada 9 September 2020Verywell Family. https://www.verywellfamily.com/31-weeks-pregnant-4159202
Diakses pada 9 September 2020Ophthalmic Plastic and Reconstructive Surgery. https://journals.lww.com/op-rs/Fulltext/2016/11000/Embryologic_and_Fetal_Development_of_the_Human.1.aspx
Diakses pada 9 September 2020