Field studies of psychologically targeted ads face threats to internal validity.

@article{Eckles2018FieldSO,
  title={Field studies of psychologically targeted ads face threats to internal validity.},
  author={Dean Eckles and Brett R. Gordon and Garrett A. Johnson},
  journal={Proceedings of the National Academy of Sciences of the United States of America},
  year={2018},
  volume={115 23},
  pages={
          E5254-E5255
        }
}