@article{411903,
      author = {Evenson, Robert E. and Gollin, Douglas.},
      url = {http://library.usi.edu/record/411903},
      title = {Crop variety improvement and its effect on productivity  the impact of international agricultural research /  [electronic resource] :},
      publisher = {CABI Pub.,},
      recid = {411903},
      pages = {xxv, 522 p. :},
      address = {Wallingford, Oxon, UK ;},
      year = {2003},
}