Fix understanding links

README.md

@@ -333,13 +333,13 @@ Congratulations! You've just developed a RESTful web service with Spring.
 
 
 
-[u-rest] /understanding/REST
-[u-json] /understanding/JSON
-[u-view-templates] /understanding/view-templates
+[u-rest]: /understanding/REST
+[u-json]: /understanding/JSON
+[u-view-templates]: /understanding/view-templates
 [jackson]: http://wiki.fasterxml.com/JacksonHome
-[u-war] /understanding/WAR
-[u-tomcat] /understanding/Tomcat
-[u-application-context] /understanding/application-context
+[u-war]: /understanding/WAR
+[u-tomcat]: /understanding/Tomcat
+[u-application-context]: /understanding/application-context
 [`@Controller`]: http://static.springsource.org/spring/docs/current/javadoc-api/org/springframework/stereotype/Controller.html
 [`SpringApplication`]: http://static.springsource.org/spring-bootstrap/docs/0.5.0.BUILD-SNAPSHOT/javadoc-api/org/springframework/bootstrap/SpringApplication.html
 [`@EnableAutoConfiguration`]: http://static.springsource.org/spring-bootstrap/docs/0.5.0.BUILD-SNAPSHOT/javadoc-api/org/springframework/bootstrap/context/annotation/SpringApplication.html