How to prove you're not already getting Kindergeld - Hamburg

Hello,
I wonder if anyone can help me with this situation?I moved to Hamburg 4 years ago and my daughter was born here in 2006.I applied for Kindergeld shortly after the birth and received it without any problems.Last March 2008 we left Hamburg and moved to the states for 6 weeks and then back and forth to Hamburg.As I was unsure of my situation I cancelled the Kindergeld in March.
I moved back to Hamburg in September and I have reapplied for the Kindergeld.This time they want proof that I have not claimed elsewhere.I did not work between the period from March till September and did not reside permantley in 1 place.Where I am supposed to get this proof from? Any advice would be much appreciated.

When we got ours I asked the UK child benefit people for a letter that they sent me and this was enough.

Ask for letters from both authorities where you were living confirming you weren't claiming.