effective synthesis of cyclobutene - see J. Salaün et A. Fade, <i><a rel="nofollow" class="external text" href="http://www.orgsyn.org/demo.aspx?prep=cv7p0117">Cyclobutene</a></i>, <a href="//commons.wikimedia.org/w/index.php?title=Org._Synth.&amp;action=edit&amp;redlink=1" class="new" title="Org. Synth. (page does not exist)">Org. Synth.</a>, 1986, vol. 64, p. 50. <a href="https://en.wikipedia.org/wiki/Digital_object_identifier" class="extiw" title="w:Digital object identifier">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.15227%2Forgsyn.064.0050">10.15227/orgsyn.064.0050</a>.
<a href="//commons.wikimedia.org/wiki/User:The_Titou" title="User:The Titou">The Titou</a>
<span class="int-own-work" lang="en">Own work</span>