(1) updated book links; (2) Fixed a cons notation

README.md

@@ -12,7 +12,7 @@ This book introduces about elementary functional algorithms and data structures.
 Contents
 --------
 
-I am adding exercises and answers to the **second edition** from 2023/03 (added 120 answers as of 2023/10). I wrote the first edition from 2009 to 2017, then rewrote from 2020 to 2023. The PDF can be **downloaded** ([EN](https://github.com/liuxinyu95/AlgoXY/files/12855002/algoxy-en.pdf), [中文](https://github.com/liuxinyu95/AlgoXY/files/12855005/algoxy-zh-cn.pdf)). The 1st edition in Chinese ([中文](https://book.douban.com/subject/26931430/)) was published in 2017. I switched my focus to the mathematics of programming from 2018, see ([github](https://github.com/liuxinyu95/unplugged)).
+I am adding exercises and answers to the **second edition** from 2023/03 (added 120 answers as of 2023/10). I wrote the first edition from 2009 to 2017, then rewrote from 2020 to 2023. The PDF can be **downloaded** ([EN](https://github.com/liuxinyu95/AlgoXY/files/13211742/algoxy-en.pdf), [中文](https://github.com/liuxinyu95/AlgoXY/files/13211747/algoxy-zh-cn.pdf)). The 1st edition in Chinese ([中文](https://book.douban.com/subject/26931430/)) was published in 2017. I switched my focus to the mathematics of programming from 2018, see ([github](https://github.com/liuxinyu95/unplugged)).
 
 
 - Preface

others/appendix/list/list-en.tex

@@ -179,7 +179,7 @@ \subsection{Last}
 &
   \begin{array}{rcl}
   init\ [x] & = & [\ ] \\
-  init\ (x:xs) & = & x : init\ xs \\
+  init\ (x \cons xs) & = & x : init\ xs \\
   \end{array}
 \end{array}
 \label{eq:list-last}

others/appendix/list/list-zh-cn.tex

@@ -181,7 +181,7 @@ \subsection{末尾元素}
 &
   \begin{array}{rcl}
   init\ [x] & = & [\ ] \\
-  init\ (x:xs) & = & x : init\ xs \\
+  init\ (x \cons xs) & = & x : init\ xs \\
   \end{array}
 \end{array}
 \label{eq:list-last}