For Each dr As DataRow In dt_art2.Rows
            aid = dr(0)
            pid = dr(1)
            ber = dr(2)
            ebn = dr(3)
            bez = dr(4)
            meng = dr(5)
            vpe = dr(6)
            ek1 = dr(7)
            vk1 = dr(8)
            bmdt = dr(9)
            bist = dr(10)
            hch1 = dr(11)
            T1 = New tvw_art_schema(aid, pid, ber, ebn, bez, meng, vpe, ek1, _
              vk1, bmdt, bist, hch)
            T1.Text = bez
            Form1.tvw_art.Nodes.Add(T1)
            For Each dr1 As DataRow In dt_art3.Rows
                l2_aid = dr1(0)
                l2_pid = dr1(1)
                l2_ber = dr1(2)
                l2_ebn = dr1(3)
                l2_bez = dr1(4)
                l2_meng = dr1(5)
                l2_vpe = dr1(6)
                l2_ek1 = dr1(7)
                l2_vk1 = dr1(8)
                l2_bmdt = dr1(9)
                l2_bist = dr1(10)
                l2_hch1 = dr1(11)
                If aid = l2_pid Then
                    T2 = New tvw_art_schema(l2_aid, l2_pid, l2_ber, l2_ebn, _
                      l2_bez, l2_meng, l2_vpe, l2_ek1, l2_vk1, l2_bmdt, _
                      l2_bist, l2_hch1)
                    T2.Text = l2_bez
                    T1.Nodes.Add(T2)
                    ....usw