 Many variants of the classical naive and TAP (i.e., second-order) mean field approximations have been proposed , each of which makes unique assumptions about the temporal evolution of the system's correlation structure .
<meaning-changed>  Many variants of the classical naive and TAP (i.e., second-order) mean field approximations have been proposed , each of which makes unique assumptions about the temporal evolution of the system's correlation structure .
 Many variants of the classical naive and TAP (i.e., second-order) mean field approximations have been proposed for their analysis, each based on unique assumptions about the temporal evolution of the system's correlation structure .