1. Pfizer. The value of vaccines in disease prevention. Pfizer: value of medicines; 2015. p. 1–3. [accessed 2016 Jul 12]. http://www.pfizer.com/files/health/VOMPaper_Vaccines_R7.pdf
2. Praveen B. Cold chain qualification. Fierce Market Place Pharma Tech; 2015. [accessed 2016 Jul 21]. http://www.stemart.com/Library/Biobanking/Cold Chain Qualification: Questions You Must Ask When Shipping Biologics.pdf
3. Federal Ministry of Health. National Primary Health Care Development Agency; National Routine Immunization Strategic Plan 2013-2015; Nigeria; 2013-2015. p. 13–27. [accessed 2016 Oct 7]. http://www.nationalplanningcycles.org/
4. Arora V Quality assurance plan for a vaccine preventable diseases surveillance program. Texas Medical Center Dissertations (via ProQuest); 2009. AAI1462271. [accessed 2017 Apr 2]. http://www.digitalcommons.library.tmc.edu/dissertations/AAI1462271