According to Nelson and Sassi, "knowledge of pedagogical process and content knowledge must be fused" in both understanding teaching and observing teaching. For example, an instructional coach working with a math teacher should know "current mathematics education reform efforts are built on the notion that the ideas in a subject, and the ways in which students and teachers work with the ideas, matter". A deep pedagogical knowledge and deep content specific knowledge are required for the teacher to have confidence in the coach and for the coach to be able to step in and assume the role of the teacher.