grap (pic preprocessor) information needed

[Ray Jones]

 The pre processor for pic, "grap" came with my version of the text
processing software for Unix.  However, the only information I have is
the man page.  

The man page only tells me that .G1 and .G2 must surround the data
points.  This is about as much as the "pic" man page - tells me almost
nothing.
 Does anyone have a short tutorial, book recommendation or even a set 
of examples of grap input files?

Your input would be much appreciated.
Thanks
-- 
Onager Systems			 Ray A. Jones
18710 NE 59th Ct.		UUCP .....uunet!camco!onager!ray
# 2053       			...ray at onager.Celestial.COM
Redmond, WA 98052               206-885-3568