Analysis of information sources in references of the Wikipedia article "Louis Diat" in English language version.
In 1947, LOUIS DIAT ("Tomatoes," page 135) of The Ritz-Carlton became gourmet's in-house chef ...
The date of this invention is generally given as 1910. But according to an old edition of Vanity Fair, the soup was presented at the opening of the hotel's roof garden. That event took place in June 1917.