WORKING GROUP 3 Building structures in mathematical knowledge CONTENTS Building structures in mathematical knowledge 287 Milan Hejný, Graham Littler, Ladislav Kvasz, Dvora Peretz Building structure in mathematics within teaching and learning processes - a study on teachers’ input and students’ achievement 290 Astrid Brinkmann The metaphor “contracts to deal with concepts” as a structuring tool in algebra 300 Elmar Cohors-Fresenborg, Christa Kaune From experience, through generic models to abstract knowledge 311 Milan Hejný, Jana Kratochvílová Classification leading to structure 321 Darina Jirotková, Graham H. Littler Discussing the challenge of categorising mathematical knowledge in mathematics research situations 332 Eva Knoll, Cécile Ouvrier-Buffet On linguistic aspects of structure building 342 Ladislav Kvasz Approaching the distributive law with young pupils 352 Nicolina A. Malara, Giancarlo Navarra The development of informal proportional thinking in primary school 363 Marilena Pantziara, Demetra Pitta-Pantazi 14 years old pupils’ thought processes: a case study of constructing the triangular inequality 374 Elif B. Turnuklu, Sibel Yesilder CERME 4 (2005) 285