but be warned that, unless you have a fast internet connection, this document may take several minutes to load.
You can reach the description of rap files by clicking on the link
but be warned that, unless you have a fast internet connection, this document may take several minutes to load.
You can find a similar link in the preface, in the section on interaction with readers. That link targets a document that is in your own computer and will work much more rapidly.
Do not confuse the set 
that is being defined here with the set difference 
.