http://www.routledge.com/textbooks/9780415997454/
http://highered.mcgraw-hill.com/sites/007353563x/student_view0/index.html
http://highered.mcgraw-hill.com/sites/0073407372/student_view0/index.html
http://www.jcu.edu/philosophy/gensler/lc/ --includes a pretest and tutor