 Another and related central philosophical topic is the critical assessment of alleged grounds for federal arrangements in general, and the division of power between member units and central bodies in particular, indicated in the preceding sections. Recent contributions include Knop et al. 1995, Kymlicka 2001, Kymlicka and Norman 2000, Nicolaidis and Howse 2001, Norman 2006. Among the important issues, especially due to the risks of instability, are: