diff --git a/README.mdown b/README.mdown
index 7f73672..acff8a2 100644
--- a/README.mdown
+++ b/README.mdown
@@ -57,5 +57,6 @@ Special Thanks
 
 * [An original git-now idea](http://d.hatena.ne.jp/sinsoku/20101208/1291770514) (by [Toshiyuki Kawanishi](https://github.com/toshi-kawanishi))
 * [Installation with homebrew](http://d.hatena.ne.jp/nobeans/20110322/1300776839) (by [Yasuharu NAKANO](https://github.com/nobeans))
+* [Referred to shell scripts](https://github.com/nvie/gitflow) (by [Vincent Driessen](https://github.com/nvie))
 
 
diff --git a/git-now-grep b/git-now-grep
index d1d6e56..a070fb3 100644
--- a/git-now-grep
+++ b/git-now-grep
@@ -1,5 +1,5 @@
 usage() {
-  echo "usage: git now grep [<base_branch>]"
+  echo "usage: git now grep [<base-branch>]"
 }
 
 cmd_default() {
diff --git a/git-now-rebase b/git-now-rebase
index 0d28509..702539e 100644
--- a/git-now-rebase
+++ b/git-now-rebase
@@ -1,6 +1,6 @@
 usage() {
-  echo "usage: git now rebase [<base_branch>]"
-  echo "       git now rebase --push|-p [--remote|-r <remote>] [<base_branch>]"
+  echo "usage: git now rebase [<base-branch>]"
+  echo "       git now rebase --push|-p [--remote|-r <remote>] [<base-branch>]"
 }