Nested numbered lists

Hi,

How do I create a numbered list with sub-lists like

1. Item one
   1.1  sub-item one
   1.2  sub-item two
        1.2.1  sub-sub-item one
        1.2.2  sub-sub-item two
   1.3  sub-item three
2. Item two
   2.1  sub-item one
   2.2  sub-item two

I looked at the setup and source code files for the "doc" and "report"
packages, in the lout/include directory, but could not see how the
existing list formats are constructed.

Lout is very impressive! Thanks for your work on this software.

Regards,

Paul Zarucki.