Pope Pius XI
Quadragesimo Anno §93
Quadragesimo Anno: On Reconstruction of the Social Order
93 The associations, or corporations, are composed of delegates from the two syndicates (that is, of workers and employers) respectively of the same industry or profession and, as true and proper organs and institutions of the State, they direct the syndicates and coordinate their activities in matters of common interest toward one and the same end.
Source: Quadragesimo Anno (Vatican.va)