THE ROLE AND FUNCTION OF PROOF WITH SKETCHPAD ('99, pdf) (The traditional view that the only function of proof is that of verification is criticised, and it is argued that other important functions of proof such as explanation, discovery, systematization, etc. ought not to be neglected in the classroom).

THE ROLE AND FUNCTION OF PROOF IN MATHEMATICS ('90, pdf) (From Pythagoras, No. 24, Nov. 1990, pp. 17-24) (Original version of above article).

EL PAPEL Y LA FUNCION DE LA DEMOSTRACION EN MATEMATICAS ('93, pdf) (Spanish translation of above article from Epsilon, No. 24, 1993, pp. 15-30)

PAPEL E FUNCOES DA DEMOSTRACAO NO TRABALHO COM O SKETCHPAD ('01, pdf) (Portuguese translation of '99 Proof article from Educacao e Matematica, No. 62, April 2001, pp. 31-36)

CHILDREN'S ACCEPTANCE OF THEOREMS IN GEOMETRY (pdf) (Some empirical data from a questionnaire regarding the grounds of children's acceptance of the truth of some geometric theorems. Poster paper presented at PME 16, 1992).

WHY PROOF IN DYNAMIC GEOMETRY? (pdf file) (A short discussion of why proof is still necessary and useful in a convincing environment such as dynamic geometry).

PUPILS' NEEDS FOR CONVICTION & EXPLANATION WITHIN GEOMETRY (pdf) (Revised and expanded version of PME 15 paper, 1991)

LEARNERS' NEEDS FOR CONVICTION AND EXPLANATION WITHIN THE CONTEXT OF DYNAMIC GEOMETRY 2000 (An empirical master's study related to students' experience of a Sketchpad activity).

TO TEACH DEFINITIONS IN GEOMETRY OR TEACH TO DEFINE? (PME '98 paper) (Distinguishes two different types of defining and present some empirical data related to a teaching experiment that focussed on defining as a process).

THE ROLE OF AXIOMATIZATION IN MATHEMATICS & MATHEMATICS TEACHING ('86, pdf) (Two different types of axiomatization are analysed in relation to their functions in mathematics and mathematics education).

ALTERNATIVE INSTRUCTIONAL STRATEGIES FOR GEOMETRY EDUCATION: A THEORETICAL STUDY (1977/8) (The theoretical background to the University of Stellenbosch Experiment in Mathematic Education (USEME) project in 1977/1978 in the Cape Province).

A FIBONACCI GENERALIZATION: A LAKATOSIAN EXAMPLE (PME '97 paper - pdf file) (Describes a generalization of the Fibonacci series which followed a Lakatosian path, and includes some philosophical comments).

FUTURE OF SECONDARY SCHOOL GEOMETRY (SOSI '96 Plenary, pdf) (Outlines recent developments in geometry research, the Van Hiele theory and the impact of dynamic geometry on the possible future of secondary school geometry).

EL FUTURO DE LA GEOMETRIA EN SECUNDARIA ('99, pdf) (Spanish translation by Martin Acosta of article "The Future of Secondary School Geometry" from Proof Newsletter, Nov/Dec 1999)

COMPUTER VERIFICATION V.S. ALGEBRAIC EXPLANATION (pdf file) (A simple junior high school example to illustrate the difference between verification and explanation).

OLYMPIC MATHEMATICS: IS IT FAIR? ('96, pdf) (Discusses the 1996 Women's 100 m. final at the 1996 Atlanta Olympic Games and whether the gold medal was awarded fairly).

TRANSFORMATIONS: A GOLDEN THREAD IN SCHOOL MATHEMATICS 1993 (pdf) (Discusses and illustrates various examples of the application of transformations such as isometries, similarities and affinities to the study of the symmetry of border patterns, tessellations, graphs and the production of alternative proofs and definitions). (Apologies for poor quality of reproduction & some typos)

THE ROLE OF TECHNOLOGY IN MATHEMATICAL MODELLING 1994 (pdf) (Various examples of the use of technology such as graphing calculators, Sketchpad and symbolic algebra software in the modelling and solution of some real world problems are given).