javadoc: links added

java/java-impl/src/com/intellij/openapi/roots/ProjectModelModificationService.java

@@ -31,6 +31,8 @@ import java.util.Collections;
  * project model. Since importing the changes to IDEA's project model may take a while the method work asynchronously and returns
  * {@link Promise} objects which may be used to be notified when the project configuration is finally updated.
  *
+ * @see ProjectModelModifier
+ *
  * @author nik
  */
 public abstract class ProjectModelModificationService {

java/java-impl/src/com/intellij/openapi/roots/ProjectModelModifier.java

@@ -29,6 +29,8 @@ import java.util.Collection;
  * The default implementation which modify IDEA's project model directly is registered as the last extension so it'll be executed if all other
  * extensions refuse to handle modification by returning {@code null}.
  *
+ * @see ProjectModelModificationService
+ *
  * @author nik
  */
 public abstract class ProjectModelModifier {