> However, the official definition of V4 (unlike the earlier versions,
> whose definitions were, I think, available only in an expensive book
> from X/Open^H^H^H^H^H^HThe Open Group) is in RFC 1813, although it's
> expressed as a delta from NLM V3 (see previous parenthetical note about
> expensive books).
It's not expensive any more:
http://www.opengroup.org/onlinepubs/009629799/toc.htm
"Open Group Technical Standard
Protocols for Interworking: XNFS, Version 3W"
"Version 3W" means "this has NFS V2 and V3, including WebNFS".
If you can't just follow the link above because it doesn't just let you
in (they may want you to "understand and accept The Open Group terms for
accessing this document", which will give you a cookie that lets you
read that document), go to
http://www.opengroup.org/publications/catalog/c702.htm
and follow the link in the section that says
<BIG><BRIGHT RED>FREE</BRIGHT RED></BIG> HTML version: To see
the full text of this document on the web "continue"
and then fill out the form.