Greenberg, D. (2000). 21st Century Schools, edited transcript of a talk delivered at the April 2000 International Conference on Learning in the 21st Century. "نسخة مؤرشفة". مؤرشف من الأصل في 2016-03-03. اطلع عليه بتاريخ 2013-06-18.
web.archive.org
Greenberg, D. (2000). 21st Century Schools, edited transcript of a talk delivered at the April 2000 International Conference on Learning in the 21st Century. "نسخة مؤرشفة". مؤرشف من الأصل في 2016-03-03. اطلع عليه بتاريخ 2013-06-18.