The loaded R package versions (in the order mentioned in the chapter):
tm 0.6-1 (CRAN)
wordcloud 2.5 (CRAN)
SnowballC 0.5.1 (CRAN)
Further R packages:
coreNLP 0.4-1 (CRAN)
topicmodels 0.2-2 (CRAN)
textcat 1.0-3 (CRAN)
Further reading:
Christopher D. Manning, Hinrich Schütze (1999): Foundations of Statistical Natural Language Processing. MIT.
Daniel Jurafsky, James H. Martin (2009): Speech and Language Processing. Prentice Hall.
Christopher D. Manning, Prabhakar Raghavan, Hinrich Schütze (2008): Introduction to Information Retrieval. Cambridge University Press. http://nlp.stanford.edu/IR-book/html/htmledition/irbook.html
Ingo Feinerer: Introduction to the tm Package Text Mining in R. https://cran.r-project.org/web/packages/tm/vignettes/tm.pdf
Ingo Feinerer (2008): A Text Mining Framework in R and Its Applications. http://epub.wu.ac.at/1923/1/document.pdf
Yanchang Zhao: Text Mining with R: Twitter Data Analysis. http://www.rdatamining.com/docs/text-mining-with-r-of-twitter-data-analysis
Stefan Thomas Gries (2009): Quantitative Corpus Linguistics with R: A Practical Introduction. Routledge.