Müller, W., Schäfer, R., &; Bleul, S. (2004). Interactive Multimodal User Interfaces for Mobile Devices. Proceedings of HICCS-37. 37th Annual Hawaii International Conference on System Sciences, Waikoloa, HI, USA.https://doi.org/10.1109/HICSS.2004.1265674 

Dücker, M., Müller, W., &; Rubart, J. (1998). VIPspace - A Visually Programmable Shared Workspace. https://doi.org/10.1109/VL.1998.706150__Proceedings. 1998 IEEE Symposium on Visual Languages . 1998 IEEE Symposium on Visual Languages , Halifax, NS, Canada .https://doi.org/10.1109/VL.1998.706150