What does $E^{2}$ mean in this context?

Question

Let $P_{i} \in E^{2}$ be the vector location of demand point $i, i = 1,..., n$

What is $E^{2}$?

Found it in a journal paper but not sure if I can link it.

Answer 1

It is probably $\mathbb{R}^2$.

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Indeed, on the first page of the article the author says

The hub location problem on the plane $E^2 $ ...