export.png
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Icon Pack: Human-O2
Designer: schollidesign
License: GNU/GPL 
http://findicons.com

Text-x-generic_with_pencil.svg / dokumodus.png
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Designer: The people from the Tango! project
License: Creative Commons Attribution
https://commons.wikimedia.org/wiki/File:Text-x-generic_with_pencil.svg

add.png / add_small.png
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Icon Pack: Soft
Designer: Asher
License: Creative Commons Attribution (by) 
http://findicons.com

download.png / download_small.png
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Icon Pack: Soft
Designer: Asher
License: Creative Commons Attribution (by) 
http://findicons.com

Nuvola_mimetypes_pdf.png / pdf_small.png
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Designer: David Vignoni / ICON KING
License: GNU GPL 2.1 or later
https://commons.wikimedia.org/wiki/File:Nuvola_mimetypes_pdf.png

settings.png
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Designer: Pau Giner
License: Creative Commons CC0 1.0 Universal Public Domain Dedication
https://commons.wikimedia.org/wiki/File:WMF-Agora-Settings_BCBCBC.svg