Format of .DXF files?

Hi,

I have a large number of spot heights in .DXF format. I'd like to get them
into GRASS somehow. I've tried using v.in.dxf but it doesn't seem to work.
Its possible that the original files are a bit dodgy. Hence, I'd like
to examine them with the aid of SOME DOCUMENTATION ON THE DXF FORMAT.

Can anyone help here?

Thanks in advance,

Fred Watson
PhD Scholar
Civil & Envorn. Eng.
Melbourne Univ.
AUSTRALIA