set M = the sigma_Measure of S;
set F = {1} --> the sigma_Measure of S;
for x being set st x in dom ({1} --> the sigma_Measure of S) holds
ex MM being sigma_Measure of S st ({1} --> the sigma_Measure of S) . x = MM by FUNCOP_1:7;
hence ex b₁ being Function st b₁ is S -Measure_valued by Def3; :: thesis: verum