Sarajevo - The German Chancellor, Dr Helmut Kohl, paying a pre-Christmas visit to German troops in Sarajevo, told Bosnia's three ethnic communities to work with the world on cementing peace. He met all three members of Bosnian collective presidency together, and said: "What I told them was very simple: try together, that is your opportunity." Dr Kohl's one-day trip began hours after President Clinton visited US troops in Bosnia.