Healthline. https://www.healthline.com/nutrition/vitamin-b12-deficiency-symptoms
Diakses pada Oktober 2018WebMD. https://www.webmd.com/diet/vitamin-b12-deficiency-symptoms-causes
Diakses pada Oktober 2018Medical News Today. https://www.medicalnewstoday.com/articles/219822.php
Diakses pada 22 Maret 2019Healthline. https://www.healthline.com/nutrition/vitamin-b12-foods#
Diakses pada 5 November 2020NCBI. https://pubmed.ncbi.nlm.nih.gov/27928125/
Diakses pada 5 November 2020