As seen in 
- Grab the nearest book.
 - Open the book to page 23.
 - Find the fifth sentence.
 - Post the text of the sentence in your journal, along with these instructions.
 
In order to avoid considering roles such as R— we will define Inv(R) s.t. Inv(R) = R– and Inv(R–) = R.
(it’s from a paper in the proceedings of last year’s International Semantic Web Conference. I’m glad it wasn’t the fourth sentence that I had to type, since that contained some symbols that I would have had to go to the HTML spec to find out how to type)