diff --git a/README.org b/README.org
index bfeb6e7..9981db5 100644
--- a/README.org
+++ b/README.org
@@ -18,7 +18,7 @@
   - [[#a-cluster][a cluster]]
 
 * Introduction
-This is a s-expression presentation of [[http://www.graphviz.org/][AT&T GraphViz]]. 
+This is a s-expression presentation of [[http://www.graphviz.org/][AT&T GraphViz]].
 The original idea is from http://www.martin-loetzsch.de/S-DOT, but with a full compatiblity of original
 DOT syntax by following its [[https://www.graphviz.org/doc/info/lang.html][lang definition]].
 
@@ -50,7 +50,7 @@ We have a similar presentation with the original [[https://graphviz.gitlab.io/_p
   | other atom    | a node statement                   | (node-id . attribute-list)              | (node1 (:label "nice node") (:shape :box)) |
   |---------------+------------------------------------+-----------------------------------------+--------------------------------------------|
 
-  
+
 * Exported Functions
 This library created a new package named as ~:dot~, and it exports the following functions to
 convert the S-DOT expression to a file can be read as the DOT Language.
@@ -95,13 +95,13 @@ For example to render a S-DOT expression to a image file, we can run the followi
 #+end_SRC
 * Examples
 ** Preparation
-We will store all images in this section in the subdirectory ~images~ 
+We will store all images in this section in the subdirectory ~images~
 #+BEGIN_SRC lisp :load no
 (defun render-dot-demo (name s-expression)
   (dot:render-graph
-   (merge-pathnames 
+   (merge-pathnames
     (format nil "images/~a.png" name)
-    (asdf:component-pathname (asdf:find-system :dot))) 
+    (asdf:component-pathname (asdf:find-system :dot)))
    s-expression))
 #+END_SRC
 
diff --git a/dot.org b/dot.org
index 8a91c8d..3368208 100644
--- a/dot.org
+++ b/dot.org
@@ -155,8 +155,8 @@ a graph is established by a stmt_list.
 We can also apply some global configuration in a ~stmt_list~ to limit their affection scope,for example:
 #+BEGIN_SRC lisp :load no
 (render-and-open-s-dot
- (merge-pathnames 
-  #p"images/statements.png" 
+ (merge-pathnames
+  #p"images/statements.png"
   (asdf:component-pathname (asdf:find-system :dot)))
  '(:digraph nil
    (= :rankdir "LR")
@@ -207,8 +207,8 @@ There are many different kinds of statements,let's recognize them one by one.
 If a statement starts without a known keyword, then it's a node statement,for example
 #+BEGIN_SRC lisp :load no
 (render-and-open-s-dot
- (merge-pathnames 
-  #p"images/node1.png" 
+ (merge-pathnames
+  #p"images/node1.png"
   (asdf:component-pathname (asdf:find-system :dot)))
  '(:digraph nil
    (node1 (:label "nice node") (:shape :box) (:fontname "Arial") (:fontcolor "#AA0000"))))
@@ -246,8 +246,8 @@ In a s-expression, it's a list that starts with an ~edgeop~ and an ~attr_list~ a
 the rest are a list of ~node id~, for example
 #+BEGIN_SRC lisp :load no
 (render-and-open-s-dot
- (merge-pathnames 
-  #p"images/edge1.png" 
+ (merge-pathnames
+  #p"images/edge1.png"
   (asdf:component-pathname (asdf:find-system :dot)))
  '(:digraph nil
    (:-> ((arrowhead :diamond)
@@ -282,8 +282,8 @@ In a dot s-expression, it starts with keyword ~:graph~, ~:node~, ~:edge~ , and t
 in the list is the ~attr_list~(ref:attr-list),for example:
 #+begin_src lisp :load no
 (render-and-open-s-dot
- (merge-pathnames 
-  #p"images/node2.png" 
+ (merge-pathnames
+  #p"images/node2.png"
   (asdf:component-pathname (asdf:find-system :dot)))
  '(:digraph nil
    (:node
@@ -306,8 +306,8 @@ a single attribute can be applied to global environment in a statement,
 in a dot s-expression, it looks like this:
 #+BEGIN_SRC lisp :load no
 (render-and-open-s-dot
- (merge-pathnames 
-  #p"images/attr.png" 
+ (merge-pathnames
+  #p"images/attr.png"
   (asdf:component-pathname (asdf:find-system :dot)))
  '(:digraph nil
    (= :compound t)
@@ -328,8 +328,8 @@ It a subgraph's name starts with "cluster", then it has a special meaning.
 in a dot s-expression, it looks like this:
 #+BEGIN_SRC lisp :load no
 (render-and-open-s-dot
- (merge-pathnames 
-  #p"images/cluster1.png" 
+ (merge-pathnames
+  #p"images/cluster1.png"
   (asdf:component-pathname (asdf:find-system :dot)))
  '(:digraph nil
    (:subgraph cluster_1
@@ -374,9 +374,9 @@ compass_pt	:	(n | ne | e | se | s | sw | w | nw | c | _)
 In a dot s-expression, it looks like this:
 #+BEGIN_SRC lisp :load no
 (render-and-open-s-dot
- (merge-pathnames 
-  #p"images/port.png" 
-  (asdf:component-pathname (asdf:find-system :dot))) 
+ (merge-pathnames
+  #p"images/port.png"
+  (asdf:component-pathname (asdf:find-system :dot)))
  '(:digraph nil
    (:-> nil (node1 :e) node2)))
 #+END_SRC