HBO and United Broadcasting & Entertainment have decided to sell Citadel Entertainment. A release from the companies said they are “in the early stages of discussion with potential buyers.”HBO acquired the production company in 1991, and its partner joined in a few months later. The companies’ second three-year term of agreement expires Dec. 31. All projects in production and development will continue on track and the partners’ other joint ventures will remain unaffected: Anglia TV Entertainment, Itel and Cosgrove/Hall. Citadel has produced more than 65 films for various networks, including “Rasputin,” “Buffalo Soldiers” and “Gia” for HBO. UBE is one of three broadcast groups controlling ITV and is a major shareholder in U.K.’s Channel 5.