P. Singer, D. Helic, A. Hotho, and M. Strohmaier. International Conference on World Wide Web, page 1003--1013. Republic and Canton of Geneva, Switzerland, International World Wide Web Conferences Steering Committee, (2015)
H. Cramer, M. Rost, and L. Holmquist. Proceedings of the 13th International Conference on
Human Computer Interaction with Mobile Devices and
Services, page 57--66. ACM, (2011)