The exponential integral Ei(x) and numerical calculation of its inverse

The six Mathematica notebooks (extension "nb"), contain different algorithms to calculate the exponential integral Ei(X) and its inverse. The methods and all details are provided in the article "The exponential integral Ei(x) and numerical calculation of its inverse", by Ricker & Singull for Contemporary Mathematics. For just inspecting the code, without the Mathematica software, the notebooks are provided also as PDF files.