Google Books

Google Books can sometimes be handy if you need to either locate a quote or find a reference in a section of a book you don't have access to. You can search for text in Google Books.

The Google books project aims to digitise every book on the planet! However, it does not mean you can simple read a book online (which is not a good idea). Only portions of the book will be made available to you. The digitised dataset of books can be examined for the frequency of occurrence of a term. This is the Google facility called Google Ngram Viewer.