@article{helmut2014human,
  title = {Human Appropriation of Net Primary Production: Patterns, Trends, and Planetary Boundaries}
  author = {Helmut Haberl, Karl-Heinz Erb, Fridolin Krausmann},
  journal = {Annual Review of Environment and Resources},
  doi = {10.1146/annurev-environ-121912-094620},
  year = {2014}
}