Mathematical actions as procedural resources: An example from the separation of variables Michael C. Wittmann and Katrina E. Black Phys. Rev. ST Phys. Educ. Res. 11, 020114 – Published 23 September 2015 [This paper is part of the Focused Collection on Upper Division Physics Courses.] Students learning to separate variables in order to solve a read more Michael and Katrina write about resource creation in Phys Rev