Unit 2-More Learning
1.Concept to classroom
http://www.thirteen.org/edonline/concept2class/index.html
2.The Cooperative Learning Network
https://nsacoop.org/webcast_details.php?id=190
3.协作学习概念
https://baike.baidu.com/item/%E5%8D%8F%E4%BD%9C%E5%AD%A6%E4%B9%A0/1232746?fr=aladdin