APA   Click to copy
Roberts, S. G. B., & Dunbar, R. I. M. (2011). The costs of family and friends: an 18-month longitudinal study of relationship maintenance and decay. EVOLUTION AND HUMAN BEHAVIOR, 32, 186–197. https://doi.org/10.1016/j.evolhumbehav.2010.08.005

Chicago/Turabian   Click to copy
Roberts, SGB, and RIM Dunbar. “The Costs of Family and Friends: an 18-Month Longitudinal Study of Relationship Maintenance and Decay.” EVOLUTION AND HUMAN BEHAVIOR 32 (May 1, 2011): 186–197.

MLA   Click to copy
Roberts, S. GB, and R. IM Dunbar. “The Costs of Family and Friends: an 18-Month Longitudinal Study of Relationship Maintenance and Decay.” EVOLUTION AND HUMAN BEHAVIOR, vol. 32, ELSEVIER SCIENCE INC, May 2011, pp. 186–97, doi:10.1016/j.evolhumbehav.2010.08.005.

@article{roberts2011a,
  title = {The costs of family and friends: an 18-month longitudinal study of relationship maintenance and decay},
  year = {2011},
  month = may,
  day = {1},
  journal = {EVOLUTION AND HUMAN BEHAVIOR},
  pages = {186--197},
  publisher = {ELSEVIER SCIENCE INC},
  volume = {32},
  doi = {10.1016/j.evolhumbehav.2010.08.005},
  author = {Roberts, SGB and Dunbar, RIM},
  month_numeric = {5}
}