APA   Click to copy
Li, I., Dey, A. K., & Forlizzi, J. (2012). Using context to reveal factors that affect physical activity. ACM Transactions on Computer-Human Interaction, 19(1).

Chicago/Turabian   Click to copy
Li, Ian, Anind K. Dey, and Jodi Forlizzi. “Using Context to Reveal Factors That Affect Physical Activity.” ACM Transactions on Computer-Human Interaction 19, no. 1 (January 29, 2012).

MLA   Click to copy
Li, Ian, et al. “Using Context to Reveal Factors That Affect Physical Activity.” ACM Transactions on Computer-Human Interaction, vol. 19, no. 1, Jan. 2012.

@article{ian2012a,
  title = {Using context to reveal factors that affect physical activity},
  year = {2012},
  month = jan,
  day = {29},
  issue = {1},
  journal = {ACM Transactions on Computer-Human Interaction},
  volume = {19},
  author = {Li, Ian and Dey, Anind K. and Forlizzi, Jodi},
  month_numeric = {1}
}