The German Football Federation (DFB) president has sent an open letter to all 25,641 clubs in the country urging respect for referees after a volunteer linesman was beaten to death in the Netherlands.
Dutch police have arrested four players suspected of involvement in the fatal beating after a youth match.
DFB president Wolfgang Niersbach said what happened in the Netherlands must not be repeated. He said the commitment of referees in Germany "deserves the highest recognition and respect" and "our special protection."
They help oversee the nearly 1.6 million games annually in the country, he said