1. Mobile search volume more than doubles year-on-year. http://www.smartinsights.com/search-engine-optimisation-seo/seo-analytics/mobile-search-volume-more-than-doubles-year-on-year/.
2. Survey: 31 percent of u.s. internet users own tablets. http://www.pcmag.com/article2/0,2817,2405972,00.asp.
3. What you need to know about targeting ipad and tablet searchers. http://searchengineland.com/what-you-need-to-know-about-targeting-ipad-tablet-searchers-109685.
4. A. Argyriou, T. Evgeniou, and M. Pontil. Multi-task feature learning. In Advances in Neural Information Processing Systems 19. MIT Press, 2007.
5. R. Baeza-yates, G. Dupret, and J. Velasco. A study of mobile search queries in japan. In In Query Log Analysis: Social and Technological Challenges, WWW 2007, 2007.