They claim that this combined theory is useful for teachers and teacher educators, enabling one to focus on mathematical knowledge and its implementation in teaching. On the one hand, the framework allows teacher educators to give specific attention to areas of knowledge, and on the other, it helps to focus teachers’ attention on the particular knowledge they are attempting to build in their classrooms. The unique feature of this study, then, is this – the implementation of a theory of mathematics knowledge which guides reflection on teachers’ mathematical knowledge.