http://docs.google.com/viewer?a=v&q=cache:zdW-dv1-VfwJ:www.cse.dmu.ac.uk/~mward/martin/papers/middle-out-t.pdf+middle-out-t.pdf&hl=en&gl=il&pid=bl&srcid=ADGEESggUHcrEUZyUnKvbE7WOnj1XyygnPs5tSDqjK77qSIVjRLixBMUDF4QxIu1ZJx0wC3QuY-qNGZV0B_NuBsdor3RT3Wagko51NBwVV8ICjVJjI2-kX-NTxmHeHc5DzoE6teYTJTJ&sig=AHIEtbT0CS3tkp8ow-NiyLfJ1ycmNWROVQ