This image was uploaded as part of <a href="https://pl.wikipedia.org/wiki/Wikipedia:Wiki_Lubi_e-podr%C4%99czniki" class="extiw" title="pl:Wikipedia:Wiki Lubi e-podręczniki">Wiki Loves e-textbooks</a> contest in Poland.
<a href="//commons.wikimedia.org/wiki/User:Witia" title="User:Witia">Witia</a>
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<span class="int-own-work" lang="en">Own work</span>