@article{20180,
      recid = {20180},
      title = {Mathematical understanding : selected results from the  secondary assessment of mathematics /},
      publisher = {Dept. of Health, Education, and Welfare,},
      address = {[Washington :},
      pages = {xv, 40 p. :},
      year = {1979},
      url = {http://library.usi.edu/record/20180},
}