Roland Illig wrote:

>     http://people.freebsd.org/~yar/rcng/article.html
> 
> In section 3, there are some circled numbers to reference code in a 
> listing. Can we have them, too? I could make use of them in the pkgsrc 
> guide, the chapter on Makefile programming:

They are using "callouts". You can find a description here

  http://www.sagehill.net/docbookxsl/AnnotateListing.html

Before we start using them, we should (as Bob Stayton recommends)
establish naming rules for the identifiers (ie. document them) and we
need to have the small marker images (there's probably some copyright
associated with those on the FreeBSD website or on Stayton's site...).

ciao
     Klaus