*48%*:**Upper-division students' difficulties with Ampère's law***47%*:**Students’ understanding of continuous charge distributions***42%*:**Observations on student difficulties with mathematics in upper-division electricity and magnetism***40%*:**Student understanding of basic probability concepts in an upper-division thermal physics course***39%*:**Student understanding of unit vectors and coordinate systems beyond cartesian coordinates in upper division physics courses***39%*:**Using student-generated content to engage students in upper-division quantum mechanics***38%*:**Improving Student Understanding of Coulomb's Law and Gauss's Law***35%*:**Student determination of differential area elements in upper-division physics***34%*:**Student Difficulties in Understanding Probability in Quantum Mechanics***34%*:**Improving students’ understanding of quantum measurement. I. Investigation of difficulties***34%*:**Upper-Level Physics Students’ Conceptions Of Understanding***34%*:**Student understanding of the ideal gas law, Part II: A microscopic perspective***34%*:**The effect of similar surface features on students’ understanding of the interaction of charges with electric and magnetic fields***33%*:**Student understanding of the ideal gas law, Part I: A macroscopic perspective***33%*:**Investigating student ownership of projects in an upper-division physics lab course***32%*:**Tapping into Juniors’ Understanding of E&M: The Colorado Upper-Division Electrostatics (CUE) Diagnostic***32%*:**Problem-based learning in upper division courses: Student successes, perceptions, and reactions***32%*:**Analytic framework for students’ use of mathematics in upper-division physics***32%*:**Upper-Division Students' Use of Separation of Variables**