Rivera-Matos, Idalia R., and Eddy Rios-Olivares. “A Multicenter Hospital Surveillance of Invasive Streptococcus Pneumoniae, Puerto Rico, 2001”. Puerto Rico Health Sciences Journal, vol. 24, no. 3, Sept. 2005, https://prhsj.rcm.upr.edu/index.php/prhsj/article/view/351.