Chemical structures of the isomers of diazine (1: pyridazine, 2: pyrimidine, 3: pyrazine)
Ed (<a href="//commons.wikimedia.org/wiki/User_talk:Edgar181" title="User talk:Edgar181">Edgar181</a>)
2017-05-20 16:14
<span class="int-own-work" lang="en">Own work</span>