Here are some articles I've stumbled upon that analyze rap lyrics.
"I SEE DEATH AROUND THE CORNER”: NIHILISM IN RAP MUSIC" by Charis E. Kubrin
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"Changes in the prevalence of alcohol use in rap song lyrics, 1979–97" by Denise Herd
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"Changes in drug use prevalence in rap music songs, 1979–1997" also by Denise Herd
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"Tragic Narratives in Popular Culture: Depictions of Homicide in Rap Music" by Gwen Hunnicutt and Kristy Humble Andrews
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"I SEE DEATH AROUND THE CORNER”: NIHILISM IN RAP MUSIC" by Charis E. Kubrin
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"Changes in the prevalence of alcohol use in rap song lyrics, 1979–97" by Denise Herd
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"Changes in drug use prevalence in rap music songs, 1979–1997" also by Denise Herd
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"Tragic Narratives in Popular Culture: Depictions of Homicide in Rap Music" by Gwen Hunnicutt and Kristy Humble Andrews
RapidShare: 1-CLICK Web hosting - Easy Filehosting