On some symmetrical equations of the form $f_1(x_1+...+x_n) = ∑_{i_1,...,i_n}) f_1(x_i_1)...f_n(x_i_n)$
Tom 19 / 1967
Annales Polonici Mathematici 19 (1967), 271-286
DOI: 10.4064/ap-19-3-271-286
