“…Such a method was proposed and called the TT-Cross method [55]. It heavily exploits the matrix cross interpolation [57], [58], [59], [60], [61] algorithm applied cleverly, although heuristically, to selected submatrices in the unfolding matrices of the given tensor. The matrix , A k ( i 1 … i k , i k + 1 … i d ) = A ( i 1 , i 2 , … , i d ) is called the k -th unfolding matrix of the tensor A .…”