No potential conﬂict of interest was reported by the authors.
Ball, D. (2002). What do we believe about teacher learning and how we can learn with and
from our beliefs? In D. S. Mewborn, P. Sztajn, D. Y. White, H. G. Wiegel, R. L. Bryant, &
K. Nooney (Eds.), 24th annual meeting of the North American Chapter of the International
Group for the Psychology of Mathematics (pp. 2–18). Athens, GA: PME-NA.
Ball, D., Hill, H., & Bass, H. (2005). Knowing mathematics for teaching: Who knows mathematics
well enough to teach third grade. American Educator,29(1), 14–16, 20–22, 43–46.
Ball, D., Thames, M., & Phelps, G. (2008). Content knowledge for teaching: What makes it
special? Journal of Teacher Education,59(5), 389–407.
Berger, J. (2013). Contagious: Why things catch on. New York, NY: Simon & Schuster, Inc.
Bryk, A., Camburn, E., & Louis, K. S. (1999). Professional community in Chicago elementary
schools: Facilitating factors and organizational consequences. Educational Administration
Carpenter, J. P., & Krutka, D. G. (2014). How and why educators use Twitter: A survey of the
ﬁeld. Journal of Research on Technology in Education,46(4), 414–434.
Darling-Hammond, L., & Hammerness, K. (2005). The design of teacher education programs. In
L. Darling-Hammond & J. Bransford (Eds.), Preparing teachers for a changing world: What
teachers should learn and be able to do (pp. 390–441). San Francisco: Jossey-Bass.
Davis, B., & Simmt, E. (2006). Mathematics-for-teaching: An ongoing investigation of the
mathematics that teachers (need to) know. Educational Studies in Mathematics,61(3),
Duncan-Howell, J. A. (2009). Online professional communities: Understanding the eﬀects of
membership on teacher practice. The International Journal of Learning,16(5), 601–613.
Forte, A., Humphreys, M., & Park, T. (2012). Grassroots professional development: How
teachers use Twitter. In J. Breslin, N. B. Ellison, J. G. Shanahan, & Z. Tufekci (Eds.),
Proceedings of the 6th International AAAI Conference on Weblogs and Social Media (pp.
106–113). Palo Alto, CA: The AAAI Press.
Glaser, B., & Strauss, A. (1967). The discovery of grounded theory. Chicago, IL: Aldine.
Hiebert, J., & Stigler, J. W. (2000). A proposal for improving classroom teaching: Lessons from
TIMSS video study. The Elementary School Journal,101(1), 3–20.
Hill, H. C., Rowan, B., & Ball, D. L. (2005). Eﬀects of teachers’mathematical knowledge for
teaching on student achievement. American Educational Research Journal,42(2), 371–406.
Hur, J. W., & Brush, T. A. (2009). Teacher participation in online communities: Why do teachers
want to participate in self-generated online communities of K-12 teachers? Journal of
Research on Technology in Education,41(3), 279–303.
Larsen, J. (2016). Negotiating meaning: A case of teachers discussing mathematical abstrac-
tion in the blogosphere. In M. B. Wood, E. E. Turner, M. Civil, & J. A. Eli (Eds.), Proceedings of
the 38th Annual Meeting of the North American Chapter of the International Group for the
Psychology of Mathematics Education (pp. 331–338). Tucson, AZ: PME-NA.
Larsen, J., & Liljedahl, P. (2017). Exploring generative moments of interaction between
mathematics teachers on social media. In B. Kaur, W. K. Ho, T. L. Toh, & B. H. Choy (Eds.),
Proceedings of the 41st Conference on the International Group for the Psychology of
Mathematics Education (Vol.3, pp. 129–136). Singapore: PME.