The original scans for WWJ and KDKA are at David Gleason's American Radio History webpage.
In 1922, the Detroit News had more modestly claimed only that it had "installed the first transmitting set in use by any newspaper". But by 1945, ignoring numerous predecessors, WWJ's publicity department decided that it had somehow been elevated to the "World's First Station". And the advertisement's reference to "others operating under experimental and amateur licenses" cheerfully ignores the fact that, for the first year of its existence, the "Detroit News Radiophone" had itself operated, as 8MK, under an amateur station license.
Broadcasting, August 20, 1945, page 31:
1945 25th Anniversary ad for WWJ

Westinghouse was one of the most important companies in establishing radio broadcasting in the United States. But the idea that its November 2, 1920 broadcast in Pittsburgh, Pennsylvania over 8ZZ (soon to become KDKA) was the "World's First Regularly Scheduled Broadcast" has serious conflicts with reality, by ignoring many other earlier examples, some very well publicized, made by a number of other stations.
"Going Forward With Radio" as Presented by KDKA, 1946, page 2:
1946 KDKA promotion