*63%*:**Observations on student difficulties with mathematics in upper-division electricity and magnetism***51%*:**Upper-division student understanding of Coulomb's law: Difficulties with continuous charge distributions***51%*:**Student determination of differential area elements in upper-division physics***50%*:**Upper-Division Students' Use of Separation of Variables***48%*:**Adapting a theoretical framework for characterizing students' use of equations in physics problem solving***48%*:**Student Ideas around Vector Decomposition in the Upper Division***47%*:**Upper-division students' difficulties with Ampère's law***47%*:**Representation issues: Using mathematics in upper-division physics***47%*:**Using Johnson-Laird's cognitive framework of sense-making to characterize engineering students' mental representations in kinematics***46%*:**Investigating student ownership of projects in an upper-division physics lab course***46%*:**Student understanding of unit vectors and coordinate systems beyond cartesian coordinates in upper division physics courses***45%*:**Student Perspectives on Using Clickers in Upper-division Physics Courses***45%*:**A Research-Based Approach to Assessing Student Learning Issues in Upper-Division Electricity & Magnetism***45%*:**Problem-based learning in upper division courses: Student successes, perceptions, and reactions***44%*:**Student understanding of basic probability concepts in an upper-division thermal physics course***43%*:**A Cognitive Framework for Analyzing and Describing Introductory Students' Use and Understanding of Mathematics in Physics***42%*:**An Epistemic Framing Analysis of Upper-Level Physics Students' Use of Mathematics***42%*:**Student Learning In Upper-Level Thermal Physics: Comparisons And Contrasts With Students In Introductory Courses***40%*:**Constructing a Multiple-choice Assessment for Upper-division Quantum Physics from an Open-ended Tool**