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I would like to include a similar picture in my bachelor's thesis.

I am looking for tips on how to make this (or in general) diagram(s) more beautiful.

Can you recommend programs for creating such diagrams? Preferably free and runs under Linux.

enter image description here

marked as duplicate by Ryan, Vincent, DᴀʀᴛʜVᴀᴅᴇʀ, user568458, Hanna Jan 28 '14 at 15:53

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