diagram showing a (co)chain homotopy
<a href="https://en.wikipedia.org/wiki/de:User:Gunther" class="extiw" title="w:de:User:Gunther">Gunther</a> at <a href="https://en.wikipedia.org/wiki/de:" class="extiw" title="w:de:">German Wikipedia</a>
2006-07-03
<span class="int-own-work" lang="en">Own work</span> using LaTeX, dvips, pstoedit and skconvert