Wickham H (2011). “The Split-Apply-Combine Strategy for Data Analysis.” Journal of Statistical Software, 40(1), 1–29. http://www.jstatsoft.org/v40/i01/.

@Article{,
  title = {The Split-Apply-Combine Strategy for Data Analysis},
  author = {Hadley Wickham},
  journal = {Journal of Statistical Software},
  year = {2011},
  volume = {40},
  number = {1},
  pages = {1--29},
  url = {http://www.jstatsoft.org/v40/i01/},
}