Merge pull request #1372 from TrueGrom/patch-2

fix Lisp/PCL link (404 error)

free-programming-books-ru.md

@@ -135,7 +135,7 @@
 
 ### Lisp
 * [Lisp In Small Pieces (translation)](https://github.com/ilammy/lisp)
-* [Practical Common Lisp(translation)](http://lisper.ru/pcl)
+* [Practical Common Lisp(translation)](http://lisper.ru/pcl/)
 
 
 ### MetaPost