Update chapters/unitexpressions.tex

Co-authored-by: Henrik Tidefelt <henrikt@wolfram.com>

chapters/unitexpressions.tex

@@ -65,7 +65,7 @@ \section{The Syntax of Unit Expressions}\label{the-syntax-of-unit-expressions}
 The set of allowed characters is currently not defined, but it is recommended to only use \lstinline[language=grammar]!NON-DIGIT!.
 It is required that basic and derived units of the SI system are recognized, but tools are allowed to additionally support user-defined unit symbols.
 The required unit symbols do not make use of Greek letters, but a unit such as $\Omega$ is spelled out as \lstinline!"Ohm"!.
-Similarly degree is spelled out as \lstinline!deg! for angles, and \lstinline!degC!, \lstinline!degF! and \lstinline!degRk! for temperatures (Celsius, Fahrenheit and Rankine).
+Similarly degree is spelled out as \lstinline!"deg"! for angles, and \lstinline!"degC"!, \lstinline!"degF"! and \lstinline!"degRk"! for temperatures (Celsius, Fahrenheit and Rankine).
 
 A \lstinline[language=grammar]!unit-operand! should first be interpreted as a \lstinline[language=grammar]!unit-symbol! and only if not successful the second alternative assuming a prefixed operand should be exploited.
 There must be no spacing between the \lstinline[language=grammar]!unit-symbol! and a possible \lstinline[language=grammar]!unit-prefix!.