original: Chess boxing fights have been organized since early 2003.
simplifications: Chess boxing fights have existed since early 2003. Chess boxing fights have been around since 2003. Chess boxing fights were organized since 2003. Chess boxing fights have been around since 2003. Chess boxing fights have existed since early 2003. Chess boxing fights have been since early 2003. Chess boxing fights have taken place since 2003. Since 2003, Chess boxing fights have been organized. Since early 2003, chess boxing fights have been set up. Chess boxing fights have been happening since early 2003.