Last week I attended your lecture in Vlissingen where you spoke about the Singapore approach. During the lecture you mentioned some names of people who wrote about the CPA approach, the Conceptual approach and about systematic variation in your powerpoint presentation. I'm very interested in reading articles about these approaches.
Educator in the Netherlands
You can goggle Jerome Bruner (spiral curriculum, enactive-iconic-symbolic representations), Zoltan Dienes (variability) and Richard Skemp (relational understanding, instrumental understanding).
These are the key theories taught at the NIE to Singapore mathematics teachers.