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2. (2) 経済産業省 資源エネルギー庁：「水素社会実現に向けた取組」, https://www.enecho.meti.go.jp/category/saving_and_new/advanced_systems/hydrogen_society/ (in Japanese)
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5. (4) R. Bouchet, E. Siebert, and G. Vitter : “Acid‐Doped Polybenzimidazole as the Membrane of Electrochemical Hydrogen Sensors”, J. Electrochem. Soc., Vol. 144, L95 (1997)