1. (2001). Free-choice science learning: Framing the issues. In: (Ed.), Free-choice science education: How people learn science outside of school (pp. 2-9). New York: Teacher's College Press.
2. & (1998, May/June). Free-choice learning: An alternative term to informal learning? Informal Learning Environments Research Newsletter (p. 2). Washington, DC: American Educational Research Association.
3. & (2002). Lessons without limit: How free-choice learning is transforming education. Walnut Creek, CA: AltaMira.