A classical theorem on harmonic functions states that singularities of bounded harmonic functions are removable if the singular set is of null capacity. This theorem is sometimes attributed to Bouligand, and sometimes to Wiener. I have seen it proved in Wiener's 1924 paper, but I cannot find any source related to Bouligand. Can you please help me locate the original paper of Bouligand where it is proved, or a secondary source that claims Bouligand's priority? Did he prove it before 1924?
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According to Armitage and Gardiner, Classical potential theory, Springer, 2001, p.313, Bouligand has proved in [1] that if $E$ is a compact polar subset of a domain $\Omega\subset\mathbb{R}^{N}$ and if $h$ is a bounded harmonic function in $\Omega\setminus E$ then $h$ has a unique harmonic extension to $\Omega$.
[1] G. Bouligand, "Sur Ie problème de Dirichlet", Ann. Soc. Polon. Math. 4 (1926), 59-112.
