crystal structure of <a href="https://en.wikipedia.org/wiki/Barium_peroxide" class="extiw" title="en:Barium peroxide">en:Barium peroxide</a>
<a href="//commons.wikimedia.org/wiki/User:Orci" title="User:Orci">Orci</a>
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Own work, data source: W. Wong-Ng and R. S. Roth: <i>Single-crystal structural investigation of BaO<sub>2</sub>.</i> In: Physica C: Superconductivity, 1994, 233, S. 97-101.