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GAEB Converter
This tool allows the conversion between Microsoft Excel and the GAEB file formats. The Excel files can be used to calculate, analyze and share GAEB project data. Additionally, you can convert between different GAEB versions with the converter or repair GAEB files that seem to be damaged. If you want to know how to use the converter, just try it out or read the tutorial. There's another tutorial for how to work with the Excel files. The tutorial is also available in German.
The Excel files are in 
if your browsers language is German, otherwise the description will be English 
The GAEB Converter is free to use, without any liability whatsoever for the created files or their correctness. If you're interested in a .Net Library for reading and writing GAEB files, contact me! The library is available both as NuGet package and dll and is compatible with classic .Net Desktop as well as NET Standard on Windows, Linux, Mac and others.
More information is available at the libraries product site.