“The book Building the Foundation: Whole Numbers in the Primary Grades is the documentation of the 23rd ICMI study. For those not familiar with this series, ICMI (International Commission on Mathematical Instruction) studies are international conferences supported by the Executive Committee of the International Commission of Mathematics Instruction. The participants in these conferences together produce a study volume which aims to offer a coherent, state-of-the-art representation of the domain of the study.” (Jorryt van Bommel and Hanna Palmér, Educational Studies in Mathematics, Vol. 100, 2019)