@article{229663,
      recid = {229663},
      author = {Osborn, Roger.},
      title = {Understanding the number system},
      publisher = {C. E. Merrill},
      address = {Columbus, Ohio,},
      pages = {viii, 189 p.},
      year = {1968},
      note = {Revision of Toward improved understanding of mathematics,  part I, by M. V. DeVault, published in 1960, and of part of  the combined revised ed. by R. Osborn and others, published  in 1961 under the title Extending mathematics  understanding.},
      url = {http://library.usi.edu/record/229663},
}