Hello, I understand marks are important because, when the time comes to chose between applicants, GPAs are a quick tool to narrow the list. Additionally, to any credible scientist, simply claiming ability isn't enough - you need to provide some evidence. Indeed, unfortunately for me, my grades are not representative of my knowledge. For quite some time now I have been reading graduate texts on Quantum Field Theory and the like, and, in my spare time, I write old practice exams (e.g. http://www.maths.cam.ac.uk/postgrad/mathiii/pastpapers/), and do quite well on them (upwards of 95%). Where school is concerned, however, I only have a 3.03 cGPA. So, in short, my question is this: how can I properly demonstrate, when asking professors for employment, that I am a capable researcher?