Image:Hilbert curve.png

Diagram shown the first six steps of David Hilbert's space-filling curve. Drawn by Zbigniew Fiedorowicz. Taken from http://www.math.ohio-state.edu/~fiedorow/math655/Peano.html

What follows is an email to him and his reply.

Dear Dr Fiedorowicz 

Re: http://www.math.ohio-state.edu/~fiedorow/math655/Peano.gif

I am writing to you on behalf of the Wikipedia project
http://www.wikipedia.org, an endeavour to build a
fully-fledged multilingual encyclopaedia in an
entirely open manner, to ask for permission to use
your copyrighted material.

Your  website has a page on the Peano curve that has a
wonderful illustration showing the first six
iterations  which would undoubtedly enhance our page
http://en.wikipedia.org/wiki/Space-filling_curve

I should like to ask for your permission to use it
under the terms of Wikipedia's licence.

Wikipedia licenses all its content under the licence
developed for purposes of free documentation by the
Free Software Foundation, the text of which can be
found at http://www.gnu.org/copyleft/fdl.html It
should be borne in mind that if you choose to allow
Wikipedia to use the  diagram, it will remain
copyrighted to you; however, the said licence
stipulates that third parties must be permitted to
reuse the licensed work so long that they retain the
licence of this work and any derivatives from it.
Consequently, you may wish to consider carefully
whether you are prepared to compromise some of your
rights granted to you by copyright law by licensing
your work as suggested. If you do choose to give
permission we shall greatly appreciate it.

Thank you for your time and consideration.

I look forward to your reply.

Yours faithfully
Theresa Knott

His reply was

Please feel free to use it.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation license, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation license". Aragonés | العربية | Asturianu | Български | বাংলা | ইমার ঠার/বিষ্ণুপ্রিয়া মণিপুরী | Brezhoneg | Bosanski | Català | Cebuano | Česky | Dansk | Deutsch | Ελληνικά | English | Esperanto | Español | Eesti | Euskara | فارسی | Suomi | Français | Gaeilge | Galego | עברית | Hrvatski | Magyar | Bahasa Indonesia | Ido | Íslenska | Italiano | 日本語 | ქართული | ភាសាខ្មែរ | 한국어 | Kurdî / كوردی | Latina | Lëtzebuergesch | Lietuvių | Bahasa Melayu | Nnapulitano | Nederlands | ‪Norsk (nynorsk)‬ | ‪Norsk (bokmål)‬ | Occitan | Polski | Português | Română | Русский | Slovenčina | Slovenščina | Shqip | Српски / Srpski | Svenska | తెలుగు | ไทย | Türkçe | Українська | اردو | Tiếng Việt | Volapük | Yorùbá | ‪中文(中国大陆)‬ | ‪中文(台灣)‬ | +/-