Cycles

Hi,
   I was just wondering if anyone had a 'definitive' list of where it is 
possible to get a cycle in an ART.  Has anyone looked at where it is 
theoretically possible to get a cycle and what code causes it?  Or, if 
not, does anyone have a list simply from the experience of writing the 
SExp cycle detection code – I'm having a few problems deciphering 
exactly what it is looking for.

Thanks

Tom Davie

--
What is the internet?
It's the largest equivalence class in the reflexive transitive 
symmetric closure of the relationship "can be reached by an IP packet 
from". -- Seth Breidbart