Sentence:  [http://books.google.com.au/books?id=RS_MC8wb48EC&printsec=frontcover&dq=%22revision%22|%22revisions%22+-intitle:%22%22+-inauthor:%22%22&hl=en&sa=X&ei=eBwMUMzACcyciAfrkPG1DQ&redir_esc=y#v=onepage&q=%22revision%22|%22revisions%22%20-intitle%3A%22%22%20-inauthor%3A%22%22&f=false Essential <WSD>Revision</WSD> Notes in Medicine for Students] 
Meaning of the word marked with <WSD> tags:  The action or process of reviewing something previously learned, especially one′s notes in preparation for a test or examination.