diff --git a/doc/readme/pkuthss.bib b/doc/readme/pkuthss.bib
index d34fc4a..3f4adbe 100644
--- a/doc/readme/pkuthss.bib
+++ b/doc/readme/pkuthss.bib
@@ -30,7 +30,7 @@
 @online{amsthm,
 	author = {{Publications Technical Group, American Mathematical Society}},
 	title = {Using the amsthm Package},
-	edition = {Ver.\ 2.20.3},
+	edition = {Ver.~2.20.3},
 	type = {M/OL},
 	date = {2017-09},
 	url = {https://ctan.org/pkg/amsthm},
@@ -41,7 +41,7 @@
 @online{biber,
 	author = {Kime, Philip and Charette, Fran\c{c}ois},
 	title = {Biber: A backend bibliography processor for biblatex},
-	edition = {Ver.\ 2.7},
+	edition = {Ver.~2.7},
 	type = {M/OL},
 	date = {2016-12-05},
 	url = {https://ctan.org/pkg/biber},
@@ -52,7 +52,7 @@
 @online{biblatex,
 	author = {Lehman, Philipp},
 	title = {The biblatex Package: Programmable Bibliographies and Citations},
-	edition = {Ver.\ 3.7},
+	edition = {Ver.~3.7},
 	type = {M/OL},
 	date = {2016-11-16},
 	url = {https://ctan.org/pkg/biblatex},
@@ -63,7 +63,7 @@
 @online{biblatex-caspervector,
 	author = {Vector, Casper Ti.},
 	title = {biblatex 参考文献和引用样式：caspervector},
-	edition = {Ver.\ 0.3.3},
+	edition = {Ver.~0.3.3},
 	type = {M/OL},
 	date = {2018-06-29},
 	url = {https://ctan.org/pkg/biblatex-caspervector},
@@ -74,7 +74,7 @@
 @online{biblatex-gb7714-2015,
 	author = {胡振震},
 	title = {符合 GB/T 7714-2015 标准的 biblatex 参考文献样式},
-	edition = {Ver.\ 0.1w},
+	edition = {Ver.~0.1w},
 	type = {M/OL},
 	date = {2021-01-19},
 	url = {https://ctan.org/pkg/biblatex-gb7714-2015},
@@ -95,7 +95,7 @@
 @online{ctex,
 	author = {{ctex.org}},
 	title = {\CTeX 宏集手册},
-	edition = {Ver.\ 2.4.8},
+	edition = {Ver.~2.4.8},
 	type = {M/OL},
 	date = {2017-02-23},
 	url = {https://ctan.org/pkg/ctex},
@@ -116,7 +116,7 @@
 @online{fancyhdr,
 	author = {van Oostrum, Piet},
 	title = {Page layout in \hologo{LaTeX}},
-	edition = {Ver.\ 3.8},
+	edition = {Ver.~3.8},
 	type = {M/OL},
 	date = {2016-09-06},
 	url = {https://ctan.org/pkg/fancyhdr},
@@ -127,7 +127,7 @@
 @online{geometry,
 	author = {Umeki, Hideo},
 	title = {The geometry package},
-	edition = {Ver.\ 5.6},
+	edition = {Ver.~5.6},
 	type = {M/OL},
 	date = {2010-09-12},
 	url = {https://ctan.org/pkg/geometry},
@@ -148,7 +148,7 @@
 @online{hyperref,
 	author = {Rahtz, Sebastian and Oberdiek, Heiko},
 	title = {Hypertext marks in \hologo{LaTeX}: a manual for hyperref},
-	edition = {Ver.\ 6.82q},
+	edition = {Ver.~6.82q},
 	type = {M/OL},
 	date = {2012-11},
 	url = {https://ctan.org/pkg/hyperref},
@@ -159,7 +159,7 @@
 @online{latexsym,
 	author = {Mittelbach, Frank},
 	title = {The \hologo{LaTeX} symbol fonts for use with \hologo{LaTeX2e}},
-	edition = {Ver.\ 2.2e},
+	edition = {Ver.~2.2e},
 	type = {M/OL},
 	date = {1998-08-17},
 	url = {https://ctan.org/tex-archive/macros/latex/base},
@@ -190,7 +190,7 @@
 @online{subcaption,
 	author = {Sommerfeldt, Alex},
 	title = {The subcaption package},
-	edition = {Ver.\ 1.1-75},
+	edition = {Ver.~1.1-75},
 	type = {M/OL},
 	date = {2013-04-16},
 	url = {https://ctan.org/pkg/subcaption},
@@ -211,7 +211,7 @@
 @online{tocloft,
 	author = {Robertson, Will},
 	title = {The tocloft package},
-	edition = {Ver.\ 2.3f},
+	edition = {Ver.~2.3f},
 	type = {M/OL},
 	date = {2013-05-02},
 	url = {https://ctan.org/pkg/tocloft},
@@ -292,7 +292,7 @@
 @online{pku-thesisstyle,
 	author = {北京大学学位办公室},
 	title = {北京大学研究生学位论文写作指南},
-	edition = {Ver.\ 2.0},
+	edition = {Ver.~2.0},
 	type = {M/OL},
 	date = {2015-06-11},
 	url = {http://grs.pku.edu.cn/document/20150611115317661150.pdf},
diff --git a/tex/pkuthss.cls b/tex/pkuthss.cls
index e48906e..4499528 100644
--- a/tex/pkuthss.cls
+++ b/tex/pkuthss.cls
@@ -114,11 +114,11 @@
 \ifthss@opt@pkufoot
 	% Handle the `Unparsed material' issue with latex/dvipdfmx compilation.
 	\unless\ifxetex\unless\ifpdf
-		\newcommand*\pgfsysdriver{pgfsys-dvipdfm.def}
+		\newcommand*{\pgfsysdriver}{pgfsys-dvipdfm.def}
 	\fi\fi
 	% Circled text, cf. <https://tex.stackexchange.com/questions/7032/>.
 	\RequirePackage{tikz}
-	\newcommand*\thss@int@circled[1]{%
+	\newcommand*{\thss@int@circled}[1]{%
 		\scalebox{0.8}{\tikz[baseline = (char.base)]{
 			\node[
 				shape = circle, draw = black, minimum size = 1.25em, inner sep = 0pt
@@ -357,7 +357,7 @@
 \renewcommand{\maketitle}{%
 	\thss@int@pdfmark{\titlepagename}{titlepage}
 	% Make the title page centered.
-	\begin{titlepage}\begingroup\centering
+	\begin{titlepage}\centering
 		% Emblem and inscription of the university, and type of thesis.
 		{%
 			\ifthss@opt@ugly%
@@ -400,13 +400,13 @@
 		\vfill
 		% Date.
 		{\ifthss@opt@ugly\zihao{3}\else\zihao{-2}\fi\@date}
-	\par\endgroup\end{titlepage}%
+	\par\end{titlepage}%
 }
 
 % Typeset the title page for double-blind review.
 \newcommand{\makeblind}{%
 	\thss@int@pdfmark{\titlepagename}{titlepage}
-	\begin{titlepage}\begingroup\renewcommand{\thssnl}{\newline}
+	\begin{titlepage}\renewcommand{\thssnl}{\newline}
 		\centering\zihao{3}\selectfont\fangsong\vspace*{0.5cm}
 		{\zihao{-0}\heiti\cuniversity\cthesisname}\\[0.36\baselineskip]
 		{\zihao{-2}\fangsong\label@blindcover}%
@@ -420,7 +420,7 @@
 			\label@blindid	&	{\@blindid}	\\
 		\end{tabular}\par\vfill
 		{\@date}\par\vspace*{0.5cm}
-	\endgroup\end{titlepage}%
+	\end{titlepage}%
 }
 
 % Typeset the Chinese abstract.