@incollection{perona2014PortraitDistanceEstimation,
  title={Distance Estimation of an Unknown Person from a Portrait},
  author={Xavier P. Burgos-Artizzu, Matteo Ruggero Ronchi and Pietro Perona},
  booktitle={Computer Vision--ECCV 2014},
  pages={313--327},
  year={2014},
  publisher={Springer},
  doi={10.1007/978-3-319-10590-1_21}
}