On Wikipedia, it is claimed without a source that Imre Simon founded tropical mathematics.

The first work of his I was able to find on the subject is Limited subsets of a free monoid which uses the semiring $\mathbb N \cup \{\infty\}$ (together with the operations $\min$ and $+$) in the context of automata theory and formal languages and which dates back to 1978.

My questions is: Is this the first paper in which a tropical semiring is used?

EDIT: To clarify, I am not asking for the origin of the word tropical itself. That has already been answered on this website.

I am asking for the origin of tropical mathematics: that is, the study of the tropical semiring, be it in tropical geometry, algebra or analysis, and whether it was in an applied or theoretical context.

In other words, what is the first work that studies the tropical semiring?

EDIT: I have a follow-up question on the history of the subject here

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