Rohde, V., Laux, M., Bachmann, P., Herrmann, A., Weinlich, M., & Asdex Upgrade Team (1997). Direct measurement of the plasma potential in the edge of ASDEX Upgrade using a self emitting probe. Journal of Nuclear Materials, 241-243, 712-715. doi:10.1016/S0022-3115(96)00592-2.