\documentclass{article} \usepackage{agda} \begin{document} \begin{code} data αβγδεζθικλμνξρστυφχψω : Set₁ where postulate →⇒⇛⇉⇄↦⇨↠⇀⇁ : Set \end{code} \[ ∀X [ ∅ ∉ X ⇒ ∃f:X ⟶ ⋃ X\ ∀A ∈ X (f(A) ∈ A) ] \] \end{document}