. "Suppose that $X_1,...,X_n$ are Random Variables and given that there exist an $k$ where k is an integer and $1\\le k\\le n-1$ s.t. the joint distribution $F_{X_1,...,X_k}$ are independent to $F_{X_k+1,...,X_n}$, prove that for all $1\\le r \\le k\\le m\\le n-1$ the joint distribution of $X_1,...,X_r$ is independent to joint distibutions $X_{m+1},...,X_n$" . . .