Cologne, VfB Stuttgart and Bayer Leverkusen will hold a joint memorial service for their former coach Christoph Daum, who died on August 24 at the age of 70. The clubs said on Wednnnesday that the service will be held in Cologne’s stadium on September 12. They said they had “the joy and honour” to work with him and that “all three clubs, together with his family, are inviting friends and acquaintances, companions from national and international football and all football friends and fans to commemorate his life’s work. “Where he was at home, on the pitch, one last time in the RheinEnergie stadi…