Maarten W. A. Wijntjes Akihiro Sato Astrid M. L. Kappers Vincent Hayward Haptic Perception of Real and Virtual Curvature. 361-366 2008 EuroHaptics http://dx.doi.org/10.1007/978-3-540-69057-3_46 conf/haptics/2008e db/conf/haptics/eurohaptics2008.html#WijntjesSKH08