CHU, W. $\pi$-Formulae from dual series of the Dougall theorem. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 74, n. 12, p. 1686–1708, 2023. DOI: 10.37863/umzh.v74i12.6587. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/6587. Acesso em: 27 apr. 2025.