I like this article about sharing even though it’s on popsugar (gah!) but good old Laura Markham shared it on FB so can’t be that bad!
http://www.popsugar.com/moms/Should-You-Teach-Kids-Share-27333250
Also found this article ages ago about the problems with RIE. As you both know I’m basically in love with Magda Gerber but I did find this very balanced.