@article{smil2000energy,
  title = {Energy in the Twentieth Century: Resources, Conversions, Costs, Uses, and Consequences}
  author = {Smil, Vaclav},
  journal = {Annual Review of Energy and the Environment},
  url = {http://www.annualreviews.org/doi/10.1146/annurev.energy.25.1.21},
  year = {2000}
}