Assessing the potency of oral polio vaccine kept outside of the cold chain during a national immunization campaign in Chad, Zipursky, S., Boualam L., Cheikh D.O., Fournier-Caruana J., Hamid D., Janssen M, Kartoglu U., Waeterloos Geneviève, and Ronveaux O. , Vaccine, 5/8/2011, Volume 29, Issue 34, Number 5656, p.5652 - 5656, (2011)