The icons are mostly derived work from other icons. As such they are
licensed accordingly to the original license:

    Crystal: LPGL
    Nuvola: LGPL

Unless stated in this file, icons are work of enthought, and are released
under BSD-like license.
Files and orginal authors:
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enthought/block_canvas/function_tools/images:
             function_variable.png | Nuvola
            preferences_button.png | Crystal
