Mayorov, A.S., Gorbachev, R.V., Morozov, S.V., Britnell, L., Jalil, R., Ponomarenko, L.A., Blake, P., Novnselov, K.S., Watanabe, K., Taniguchi, T. and Geim, A.K. (2011) Micrometer-scale ballistic transport in encapsulated graphene at room temperature. Nano Letters, 11, 2396-2399.