Yellow Iris was both a short story and a radio play adaptation written by Agatha Christie in 1937. In 1945, she reworked the plot --changing character names, replacing Poirot with Col. Race, and altering the ending-- for the novel Sparkling Cyanide.
While in Buenos Aires, Poirot is seen reading a newspaper called "La Nación". A newspaper by that name actually existed in the 1930's when this story is set and is still printed today. Also the font used to print the name of the newspaper on top of the pages seems to be the same as in the real newspaper.
At the ending, Poirot tastes an English cuisine dish of fish and chips (known in the US as French fries), and finds it pleasingly edible, specifically the chips. The chips themselves originated in either France or Belgium, Poirot's homeland; the fish was added later on around the 16th century by English immigrants.
Hastings is reading the October 6, 1936 edition of "Daily Express".
This episode takes place in 1934 and 1936.