README.md in tree_html-0.1.8 vs README.md in tree_html-0.1.9

@@ -18,10 +18,14 @@
 
     $ gem install tree_html
 
 ## Usage
 
-In Node class, `include TreeHtml`, then implement `label_for_tree_html` and `children_for_tree_html`, then call `tree_html` on node object to get ul/li fragment, or `tree_html_full` to get a html file with pre-defined style.
+In Node class, `include TreeHtml`.
+
+Then implement `label_for_tree_html` and `children_for_tree_html` for Branch class, and `label_for_tree_html` for Leaf class.
+
+Finally, call `tree_html` on node object to get ul/li fragment, or `tree_html_full` to get a html file with pre-defined style.
 
 By Default, any object can be leaf, and renders as `to_s`.
 
 You may overwrite `data_for_tree_html`, `head_js_for_tree_html`, `body_js_for_tree_html`, `css_for_tree_html` to specify your own style.