Leslie Steffe earned his Ph.D. in mathematics education in 1966 from the University of Wisconsin working under the direction of Henry Van Engen. He joined the faculty of mathematics education at the University of Georgia in 1967, where he was appointed Distinguished Research Professor in 1985. Along with Ernst von Glasersfeld and John Richards, a philosopher of mathematics, he established the research program, Interdisciplinary Research on Number (IRON), circa 1976, which continues on through the present time. The book, *Children’s Fractional Knowledge*, published by Springer in 2010, is one of the latest publications of this research program.

Cobb P. & Steffe L. P. (1983) The constructivist researcher as teacher and model builder. Journal for Research in Mathematics Education 14(2): 83–94.

Olive J. & Steffe L. P. (2002) The construction of an iterative fractional scheme: The case of Joe. Journal of Mathematical Behavior 20: 413–437.

Riegler A. & Steffe L. P. (2014) “What is the teacher trying to teach students if they are all busy constructing their own private worlds?”: Introduction to the special issue. Constructivist Foundations 9(3): 297–301.

Riegler A. & Steffe L. P. (eds.) (2014) Forty years of radical constructivism in educational research. Constructivist Foundations 9(3).

Steffe L. P. (1991) (ed.) Epistemological foundations of mathematical experience. Springer, New York.

Steffe L. P. (1991) The constructivist teaching experiment: Illustrations and implications. In: Glasersfeld E. von (ed.) Radical constructivism in mathematics education. Kluwer, Dordrecht: 177–194.

Steffe L. P. (1991) The learning paradox: A plausible counterexample. In: Steffe L. P. (ed.) Epistemological foundations of mathematical experience. Springer, New York: 26–44.

Steffe L. P. (1992) Schemes of action and operation involving composite units. Learning and Individual Differences 4(3): 259–309.

Steffe L. P. (1994) Children’s multiplying schemes. In: Harel G. & Confrey J. (eds.) The development of multiplicative reasoning in the learning of mathematics. SUNY Press, New York: 3–39.

Steffe L. P. (1995) Alternative epistemologies: An educator’s perspective. In: Steffe L. P. & Gale J. (eds) Constructivism in education. Lawrence Erlbaum, Hillsdale NJ: 489–523.

Steffe L. P. (1996) Radical constructivism: A way of knowing and learning (Review of the same title, by Ernst von Glasersfeld). Zentralblatt für Didaktik der Mathematik (International Reviews on Mathematical Education) 96(6): 202–204.

Steffe L. P. (1996) Social-cultural approaches in early childhood mathematics education: A discussion. In: Mansfield H., Pateman N. A. & Bednarz N. (eds.) Mathematics for tomorrow’s young children. Kluwer, Dordrecht: 79–99.

Steffe L. P. (2000) Perspectives on issues concerning the self, paideia, constraints, viability, and ethics. In: Steffe L. P. & Thompson P. W. (eds.) Radical constructivism in action: Building on the pioneering work of Ernst von Glasersfeld. Routledge, London: 91–102.

Steffe L. P. (2002) A new hypothesis concerning children’s fractional knowledge. Journal of Mathematical Behavior 20(3): 267–307. Available at http://cepa.info/1056

Steffe L. P. (2003) The fractional composition, commensurate fractional, and the common partitioning schemes of Jason and Laura: Grade 5. Journal of Mathematical Behavior (22): 237–295.

Steffe L. P. (2004) On the construction of learning trajectories of children: The case of commensurate fractions. Mathematical Thinking and Learning 6(2): 129–162.

Steffe L. P. (2007) Radical constructivism and “school mathematics.” In: Glasersfeld E. von, Key works in radical constructivism. Edited by Marie Larochelle. Sense Publishers, Rotterdam: 279–289.

Steffe L. P. (2007) Radical Constructivism: A Scientific Research Program. Constructivist Foundations 2(2-3): 41–49. Available at http://www.univie.ac.at/constructivism/journal/2/2-3/041.steffe

Steffe L. P. (2008) “Mathematical” Schemes as Instruments of Interaction. Constructivist Foundations 3(2): 74–76. Available at http://www.univie.ac.at/constructivism/journal/3/2/074.steffe

Steffe L. P. (2010) Consequences of Rejecting Constructivism: “Hold Tight and Pedal Fast”. Commentary on Slezak’s “Radical Constructivism: Epistemology, Education and Dynamite”. Constructivist Foundations 6(1): 112–119. Available at http://www.univie.ac.at/constructivism/journal/6/1/112.steffe

Steffe L. P. (2010) Perspectives on collaborative research in mathematics education with interdisciplinary connections. In: Chamberlin S. A. & Hatfield L. L. (eds.) New perspectives and directions for collaborative research in mathematics education: Papers from a planning conference for WISDOMe. WISDOMe Monograph Volume 1. College of Education, University of Wyoming, Laramie WY: 11–28. Available at http://www.uwyo.edu/wisdome/publications/monographs/PerspectivesOnCollaboration_Steffe.pdf

Steffe L. P. (2011) The honor of working with Ernst von Glasersfeld. Partial recollections. Constructivist Foundations 6(2): 172–176. Available at http://www.univie.ac.at/constructivism/journal/6/2/172.steffe

Steffe L. P. (2014) Constructing models of ethical knowledge: A scientific enterprise. Constructivist Foundations 9(2): 262–264. Available at http://www.univie.ac.at/constructivism/journal/9/2/262.steffe

Steffe L. P. & Cobb P. (1983) The constructivist researcher as teacher and model builder. Journal for Research in Mathematics Education 14(2): 83–94.

Steffe L. P. & Cobb P. (1988) Construction of arithmetical meanings and strategies. Springer, New York.

Steffe L. P., Cobb P. & Glasersfeld E. von (1988) Construction of arithmetical meanings and strategies. Springer, New York.

Steffe L. P. & D’Ambrosio B. (1995) Toward a working model of constructivist teaching: A reaction to Simon. Journal for Research in Mathematics Education 26: 146–159.

Steffe L. P. & Gale J. (eds.) (1995) Constructivism in education. Lawrence Erlbaum, Hillsdale NJ.

Steffe L. P., Glasersfeld E. von, Richards J. & Cobb P. (1983) Children's counting types: Philosophy, theory, and application. Praeger, New York.

Steffe L. P. & Hirstein J. & Spikes C. (1976) Quantitative comparison and class inclusion as readiness variables for learning first grade arithmetic content. Technical Report No. 9. ERIC Document Reproduction Service No. ED144808. Project for Mathematical Development of Children, Tallahassee, FL.

Steffe L. P. & Kieren T. (1994) Radical constructivism and mathematics education. Journal for Research in Mathematics Education 25(6): 711–733.

Steffe L. P., Nesher P., Cobb P., Goldin G. A. & Greer B. (eds.) (1996) Theories of mathematical learning. Lawrence Erlbaum, Mahwah NJ: 449–463.

Steffe L. P. & Olive J. (2010) Children’s fractional knowledge. Springer, New York.

Steffe L. P., Richards J., Glasersfeld, von E., Y Cobb P. (1983) Children’s counting types: Philosophy, theory, and application. Praeger, New York.

Steffe L. P. & Thompson P. W. (2000) Interaction or intersubjectivity? A reply to Lerman. Journal for Research in Mathematics Education 31(2): 191–209.

Steffe L. P. & Thompson P. W. (2000) Teaching experiment methodology: Underlying principles and essential elements. In: Lesh R. & Kelly A. E. (eds.) Research design in mathematics and science education. Lawrence Erlbaum, Hillsdale NJ: 267–307.

Steffe L. P. & Thompson P. W. (eds.) (2000) Radical constructivism in action: Building on the pioneering work of Ernst von Glasersfeld. Falmer Press, London.

Steffe L. P. & Tzur R. (1994) Interaction and children’s mathematics. In: Ernest P. (ed.) Constructing mathematical knowledge: Epistemology and mathematics education. Falmer Press, London: 8–32.

Steffe L. P. & Ulrich C. (2014) The constructivist teaching experiment. In: Lerman S. (ed.) Encyclopedia of mathematics education. Springer, Berlin.

Steffe L. P. & Woods T. (eds.) (1990) Transforming children’s mathematics education: International perspective. Erlbaum, Hillsdale NJ.