The R Book
http://www.kharms.biology.lsu.edu/CrawleyMJ_TheRBook.pdf
An Introduction to R
http://cran.r-project.org/doc/manuals/R-intro.pdf
The R Guide
http://cran.r-project.org/doc/contrib/Owen-TheRGuide.pdf
Using R for Data Analysis and Graphics
http://cran.r-project.org/doc/contrib/usingR.pdf
Introduction to the R Project for Statistical Computing for use at ITC
http://cran.r-project.org/doc/contrib/Rossiter-RIntro-ITC.pdf
An Introduction to R: Software for Statistical Modeling & Computing
http://www2.ims.nus.edu.sg/preprints/2006-34.pdf
