Hello I am looking for a paper that discusses the mathematics behind the special/general theories of relativity. The majority of the papers I have come across so far discuss the principals of relativity and do not support it with mathematical conclusions. One of the papers I am looking for is by H.A. Lorentz, H. Minkowski, and A. Einstein. I think the paper was published under the title Das Relativitdtsprinsip (The Principal of Relativity). Also, if someone could point me toward a link to the original papers that Einstein published c1900 that would be much appreciated. Thanks for all your help.