title: Geographic Variation in Penicillin Resistance in Streptococcus pneumoniae: Selected Sites, United States, 1997.
abstract: [Centers for Disease Control and Prevention. Geographic variation in penicillin resistance in Streptococcus pneumoniae : selected sites, United States, 1997. MMWR Morb Mortal Wkly Rep. 1999;48:656-661.].