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Reference8 articles.
1. R. B. Burckel, “Three secrets about harmonic functions”, Am. Math. Monthly 104, 52–56 (1980).
2. D. H. Armitage and ¨U. Kuran, “The convexity of a domain and the superharmonicity of the signed distance function,” Proc. Am. Math. Soc. 93, 598–600 (1985).
3. R. J. Duffin, “Yukawan potential theory,” J. Math. Anal. Appl. 35, 105–130 (1971).
4. E. Hopf, “Elementare Bemerkungen ¨uber die L¨osungen partieller Differentialgleichungen zweiter Ordnung vom elliptischen Typus,” Sitzungsber. Preuss. Akad. Wiss., Phys.-Math. Kl. 19, 147–152 (1927).
5. D. E. Apushkinskaya and A. I. Nazarov, “The normal derivative lemma and surrounding issues,” Russ. Math. Surv. 77, No. 2, 189–249 (2022).