   ;; \omicron \Omicron
   ;; \pi \Pi
   ("Gr"  . ("ρ"))  ("GR"  . ("Ρ"))
-  ("Gs"  . ("σ"))  ("GS"  . ("Σ"))
+  ("Gs"  . ("σ"))  ("GS"  . ("Σ")) ("S"  . ("Σ"))
   ("Gt"  . ("τ"))  ("GT"  . ("Τ"))
   ("Gu"  . ("υ"))  ("GU"  . ("Υ"))
   ("Gf"  . ("φ"))  ("GF"  . ("Φ"))


  ("eq"  . ,(lean-input-to-string-list "=∼∽≈≋∻∾∿≀≃⋍≂≅ ≌≊≡≣≐≑≒≓≔≕≖≗≘≙≚≛≜≝≞≟≍≎≏≬⋕"))
  ("eqn" . ,(lean-input-to-string-list "≠≁ ≉     ≄  ≇≆  ≢                 ≭    "))

                    ("=n"  . ("≠"))
  ("~"    . ("∼"))  ("~n"  . ("≁")) ("homotopy"    . ("∼"))
  ("~~"   . ("≈"))  ("~~n" . ("≉"))
  ("~~~"  . ("≋"))
  (":~"   . ("∻"))
  ("~-"   . ("≃"))  ("~-n" . ("≄")) ("equiv"   . ("≃"))
  ("-~"   . ("≂"))
  ("~="   . ("≅"))  ("~=n" . ("≇")) ("iso"   . ("≅"))
  ("~~-"  . ("≊"))
  ("=="   . ("≡"))  ("==n" . ("≢"))
  ("==="  . ("≣"))


  ;; Various operators/symbols.
  ("tr"        . ,(lean-input-to-string-list "⬝▹"))
  ("trans"     . ,(lean-input-to-string-list "▹⬝"))
  ("transport" . ("▹"))
  ("con"       . ("⬝"))
  ("cdot"      . ("⬝"))
  ("sy"        . ("⁻¹"))
