@article{estes2006variation,
  title={Variation in pleiotropy and the mutational underpinnings of the G-matrix},
  author={Estes, Suzanne and Phillips, Patrick C},
  journal={Evolution},
  volume={60},
  number={12},
  pages={2655--2660},
  year={2006},
  publisher={Blackwell Publishing Ltd Oxford, UK}
}