archive.org
archive.org
emerald.com
dl.acm.org
ACM Digital Library
https://dl.acm.org › doi › abs › 10.5555 › 552806
dl.acm.org
ACM Digital Library
https://dl.acm.org › doi › 10.5555 › 552806
en.wikipedia.org
archive.org
nces.ed.gov
National Center for Education Statistics (NCES)
https://nces.ed.gov › pubs2003 › secureweb › ch_2.asp
archive.org
patents.google.com
patents.google.com
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