diff --git a/doc/conf.py b/doc/conf.py
index 0e57c4224677a..e8e7e2be032d5 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -193,39 +193,41 @@
     'utf8extra': r'''
         \usepackage{CJKutf8}
         \usepackage{amssymb}
+        \DeclareUnicodeCharacter{00B9}{\ensuremath{^{1}}}
         \DeclareUnicodeCharacter{00A0}{\nobreakspace}
+        \DeclareUnicodeCharacter{00D7}{\ensuremath{\times}}
+        \DeclareUnicodeCharacter{00F7}{\ensuremath{\div}}
+        \DeclareUnicodeCharacter{0127}{\ensuremath{\hbar}}
+        \DeclareUnicodeCharacter{03B3}{\ensuremath{\gamma}}
+        \DeclareUnicodeCharacter{03C0}{\ensuremath{\pi}}
+        \DeclareUnicodeCharacter{03C6}{\ensuremath{\varphi}}
+        \DeclareUnicodeCharacter{2081}{\ensuremath{_{1}}}
         \DeclareUnicodeCharacter{2203}{\ensuremath{\exists}}
         \DeclareUnicodeCharacter{2200}{\ensuremath{\forall}}
-        \DeclareUnicodeCharacter{2713}{x}
-        \DeclareUnicodeCharacter{27FA}{\ensuremath{\Longleftrightarrow}}
+        \DeclareUnicodeCharacter{2208}{\ensuremath{\in}}
+        \DeclareUnicodeCharacter{220B}{\ensuremath{\ni}}
+        \DeclareUnicodeCharacter{2209}{\ensuremath{\notin}}
+        \DeclareUnicodeCharacter{220C}{\ensuremath{\not\ni}}
+        \DeclareUnicodeCharacter{2211}{\ensuremath{\sum}}
         \DeclareUnicodeCharacter{221A}{\ensuremath{\sqrt{}}}
         \DeclareUnicodeCharacter{221B}{\ensuremath{\sqrt[3]{}}}
-        \DeclareUnicodeCharacter{2295}{\ensuremath{\oplus}}
-        \DeclareUnicodeCharacter{2297}{\ensuremath{\otimes}}
-        \DeclareUnicodeCharacter{2211}{\ensuremath{\sum}}
-        \DeclareUnicodeCharacter{03C0}{\ensuremath{\pi}}
-        \DeclareUnicodeCharacter{2081}{\ensuremath{_{1}}}
-        \DeclareUnicodeCharacter{00B9}{\ensuremath{^{1}}}
-        \DeclareUnicodeCharacter{0127}{\ensuremath{\hbar}}
+        \DeclareUnicodeCharacter{222A}{\ensuremath{\cup}}
+        \DeclareUnicodeCharacter{2229}{\ensuremath{\cap}}
+        \DeclareUnicodeCharacter{2248}{\ensuremath{\approx}}
+        \DeclareUnicodeCharacter{2249}{\ensuremath{\not\approx}}
         \DeclareUnicodeCharacter{2260}{\ensuremath{\ne}}
-        \DeclareUnicodeCharacter{2264}{\ensuremath{\le}}
-        \DeclareUnicodeCharacter{2265}{\ensuremath{\ge}}
         \DeclareUnicodeCharacter{2261}{\ensuremath{\equiv}}
         \DeclareUnicodeCharacter{2262}{\ensuremath{\not\equiv}}
-        \DeclareUnicodeCharacter{2208}{\ensuremath{\in}}
-        \DeclareUnicodeCharacter{220B}{\ensuremath{\ni}}
-        \DeclareUnicodeCharacter{2209}{\ensuremath{\notin}}
-        \DeclareUnicodeCharacter{220C}{\ensuremath{\not\ni}}
+        \DeclareUnicodeCharacter{2264}{\ensuremath{\le}}
+        \DeclareUnicodeCharacter{2265}{\ensuremath{\ge}}
         \DeclareUnicodeCharacter{2286}{\ensuremath{\subseteq}}
         \DeclareUnicodeCharacter{2288}{\ensuremath{\nsubseteq}}
         \DeclareUnicodeCharacter{228A}{\ensuremath{\subsetneq}}
-        \DeclareUnicodeCharacter{222A}{\ensuremath{\cup}}
-        \DeclareUnicodeCharacter{2229}{\ensuremath{\cap}}
-        \DeclareUnicodeCharacter{00F7}{\ensuremath{\div}}
-        \DeclareUnicodeCharacter{03B3}{\ensuremath{\gamma}}
-        \DeclareUnicodeCharacter{03C6}{\ensuremath{\varphi}}
+        \DeclareUnicodeCharacter{2295}{\ensuremath{\oplus}}
+        \DeclareUnicodeCharacter{2297}{\ensuremath{\otimes}}
         \DeclareUnicodeCharacter{22C5}{\ensuremath{\cdot}}
-        \DeclareUnicodeCharacter{00D7}{\ensuremath{\times}}
+        \DeclareUnicodeCharacter{2713}{x}
+        \DeclareUnicodeCharacter{27FA}{\ensuremath{\Longleftrightarrow}}
     ''',
 }