@article{mcfarland1987,
  title={Nursing Research: Principles and Methods},
  author={Gertrude Kay McFarland and Denise F. Polit and Bernadette P. Hungler},
  year={1987},
  journal={AJN American Journal of Nursing},
  doi={10.2307/3425916},
  url={https://doi.org/10.2307/3425916}
}