diff --git a/ack.tex b/ack.tex
index 4f05b93..cdf926e 100644
--- a/ack.tex
+++ b/ack.tex
@@ -1,11 +1,11 @@
 \chapter{附录}
 
 \section{参考文献}
-MIPS® Architecture For Programmers Volume I-A: Introduction to the MIPS32 Architecture.rev3.02
+MIPS\textsuperscript{\textregistered} Architecture For Programmers Volume I-A: Introduction to the MIPS32 Architecture.rev3.02
 
-MIPS® Architecture For Programmers Volume II-A: The MIPS32® Instruction Set 
+MIPS\textsuperscript{\textregistered} Architecture For Programmers Volume II-A: The MIPS32\textsuperscript{\textregistered} Instruction Set 
 
-MIPS® Architecture For Programmers Volume III: The MIPS32® and microMIPS32™ Privileged Resource Architecture 
+MIPS\textsuperscript{\textregistered} Architecture For Programmers Volume III: The MIPS32\textsuperscript{\textregistered} and microMIPS32\textsuperscript{\texttrademark} Privileged Resource Architecture 
 
 Xilinx IP:: AXI Crossbar (2.1) LogiCORE IP Product Guide
 
diff --git a/main.tex b/main.tex
index 12166be..d9435db 100644
--- a/main.tex
+++ b/main.tex
@@ -20,6 +20,7 @@
 \usepackage[T1]{fontenc}
 \usepackage{inconsolata}
 \usepackage{subfig}
+\usepackage{textcomp}
 
 \usepackage{amsmath}
 \usepackage{amssymb}