Katsunari Sato Hideaki Nii Naoki Kawakami Susumu Tachi Electrotactile Stimulation Based on Strain Energy Density of the Fingertip. 724-729 2008 EuroHaptics http://dx.doi.org/10.1007/978-3-540-69057-3_93 conf/haptics/2008e db/conf/haptics/eurohaptics2008.html#SatoNKT08