@inproceedings{cockburn2007,
  author	= {Andy Cockburn and Per Ola Kristensson and Jason Alexander and Shumin Zhai},
  title		= {Hard Lessons: Effort-Inducing Interfaces Benefit Spatial Learning},
  booktitle	= {Proceedings of the Conference on Human Factors in Computing Systems},
  year		= {2007},
  series	= {CHI '07},
  pages		= {1571--1580},
  address	= {New York, NY, USA},
  publisher	= {ACM},
}