Alexandra Corleis, Björn Schwarz, Gabriele Kaiser and Issic K.C. Leung have written an article called Content and pedagogical content knowledge in argumentation and proof of future teachers: a comparative case study in Germany and Hong Kong. The article was published in ZDM last week, and it provides an interesting comparison between teachers in Germany and Hong Kong. Here is the article abstract:

The results of a comparative case study on mathematical and pedagogical content knowledge in the area of argumentation and proof of future teachers in Germany and Hong Kong are reported in this article. The study forms part of a qualitatively oriented comparative study on future teachers in Australia, Germany, and Hong Kong. Six case studies based on interviews and written questionnaires are described. These case studies show the strengths of the Hong Kong future teachers in mathematical knowledge in the area of argumentation and proof, whereas the three German future teachers perform stronger in the related pedagogical content domain. Furthermore, regarding the German future teachers, it seems that the two domains of knowledge are more strongly connected to each other. The results are interpreted in the light of related research, such as the MT21 study.