About Haskell Thread Model

Hello, I am a new learner of Haskell and I am interested in Haskell's concurrent model. Can somebody give me a brief intro about Haskell's thread model, like how the use-level threads are mapped to kernel thread and what scheduling mechanism that Haskell uses, or point me to some links or documents that I can learn from. Thanks, Qing Yang qing.yang@intel.com