docs: Update documentation and Doxygen documentation generation
diff --git a/apps/ndn-consumer-zipf-mandelbrot.h b/apps/ndn-consumer-zipf-mandelbrot.h
index b9f4d17..d9333b3 100644
--- a/apps/ndn-consumer-zipf-mandelbrot.h
+++ b/apps/ndn-consumer-zipf-mandelbrot.h
@@ -38,7 +38,7 @@
 namespace ndn {
 
 /**
- * @ingroup ndn
+ * @ingroup ndn-apps
  * @brief NDN app requesting contents following Zipf-Mandelbrot Distbituion
  *
  * The class implements an app which requests contents following Zipf-Mandelbrot Distribution