`AC_LIBOBJ vs. LIBOBJS'

[Robert Collins]

I get this with automake 1.6...
configure.in:538: error: do not use LIBOBJS directly, use AC_LIBOBJ (see
section
 `AC_LIBOBJ vs. LIBOBJS'

yet the info pages don't seem to have such a section. 

Where is this documented? (And what should I change).

Rob