vi format command

[Stephen Tenbrink]

Is there a technique for reformatting a paragraph when using vi?  Sometimes
when one has deleted and added text to a paragraph the lines no longer end
near the right side of the screen.  Some editors such as EDT have a
technique of selecting the whole paragraph and then entering a command to
reformat the whole paragraph.  The word wrap margin is used to set the
right hand margin.

I'm sure there is a way to do this easier than inserting 'returns' and
using the 'J' command.  Does anyone have an answer?