  The ACL2 theorem prover is a complex system. Its libraries are vast.
Industrial verification efforts may extend this base with hundreds of thousands
of lines of additional modeling tools, specifications, and proof scripts. High
quality documentation is vital for teams that are working together on projects
of this scale. We have developed XDOC, a flexible, scalable documentation tool
for ACL2 that can incorporate the documentation for ACL2 itself, the Community
Books, and an organization's internal formal verification projects, and which
has many features that help to keep the resulting manuals up to date. Using
this tool, we have produced a comprehensive, publicly available ACL2+Books
Manual that brings better documentation to all ACL2 users. We have also
developed an extended manual for use within Centaur Technology that extends the
public manual to cover Centaur's internal books. We expect that other
organizations using ACL2 will wish to develop similarly extended manuals.
