   ("en"         . ("–"))
   ("em"         . ("—"))
   ("^i"         . ("ⁱ"))
+  ("^o"         . ("ᵒ"))
   ("!!"         . ("‼"))
   ("??"         . ("⁇"))
   ("?!"         . ("‽" "⁈"))

  ;; Types
  ("nat"  . ("ℕ"))
  ("Nat"  . ("ℕ"))
  ("int"  . ("ℤ"))
  ("Int"  . ("ℤ"))
  ("real" . ("ℝ"))
  ("Real" . ("ℝ"))

  ;; Musical symbols.


  ("increment" . ("∆"))
  ("inf"       . ("∞"))
  ("&"         . ("⅋"))
  ("op"        . ("ᵒᵖ"))

  ;; Circled operators.

