Ocfs2 devel - Apr 2009 - Where can I find formal document for DLM ?

Hi folks,

After reading some google search result and wikipedia, finally I want to ask
this question: Where can I find some formal document for DLM ?

The only document I can find is HP's How the Distributed Lock Manager (DLM)
Works. Is there any other document which people use as a spec to implement DLM ?
If yes, could you please to give me the URL.

Thanks in advance for any help :-)

-- 
Coly Li
SuSE Labs