Qiu Huang Gengsheng L. Zeng Grant T. Gullberg An Analytical Inversion of the 180degree Exponential Radon Transform with a Numerically Generated Kernel. 71-85 2007 7 Int. J. Image Graphics 1 http://dx.doi.org/10.1142/S0219467807002544 db/journals/ijig/ijig7.html#HuangZG07