APA   Click to copy
Westbrook, C., Cooper, D., & Butler, D. (2013). 12.20 Beaver Hydrology and Geomorphology.

Chicago/Turabian   Click to copy
Westbrook, C., D. Cooper, and D. Butler. “12.20 Beaver Hydrology and Geomorphology” (2013).

MLA   Click to copy
Westbrook, C., et al. 12.20 Beaver Hydrology and Geomorphology. 2013.

@article{c2013a,
  title = {12.20 Beaver Hydrology and Geomorphology},
  year = {2013},
  author = {Westbrook, C. and Cooper, D. and Butler, D.}
}