APA   Click to copy
Walker, E., Rummel, N., & Koedinger, K. R. (2009). CTRL: A research framework for providing adaptive collaborative learning support. User Modeling and User-Adapted Interaction, 19(5), 387–431.

Chicago/Turabian   Click to copy
Walker, Erin, Nikol Rummel, and Kenneth R. Koedinger. “CTRL: A Research Framework for Providing Adaptive Collaborative Learning Support.” User Modeling and User-adapted Interaction 19, no. 5 (October 30, 2009): 387–431.

MLA   Click to copy
Walker, Erin, et al. “CTRL: A Research Framework for Providing Adaptive Collaborative Learning Support.” User Modeling and User-Adapted Interaction, vol. 19, no. 5, Oct. 2009, pp. 387–431.

@article{erin2009a,
  title = {CTRL: A research framework for providing adaptive collaborative learning support},
  year = {2009},
  month = oct,
  day = {30},
  issue = {5},
  journal = {User Modeling and User-adapted Interaction},
  pages = {387-431},
  volume = {19},
  author = {Walker, Erin and Rummel, Nikol and Koedinger, Kenneth R.},
  month_numeric = {10}
}