diff --git a/gtsam/hybrid/HybridBayesNet.h b/gtsam/hybrid/HybridBayesNet.h
index c376c9a86..b19528120 100644
--- a/gtsam/hybrid/HybridBayesNet.h
+++ b/gtsam/hybrid/HybridBayesNet.h
@@ -64,6 +64,7 @@ class GTSAM_EXPORT HybridBayesNet : public BayesNet<HybridConditional> {
   GaussianBayesNet choose(const DiscreteValues &assignment) const;
 
   /// Solve the HybridBayesNet by back-substitution.
+  /// TODO(Shangjie) do we need to create a HybridGaussianBayesNet class, and put this method there?
   HybridValues optimize() const;
 };
 
diff --git a/gtsam/hybrid/HybridValues.h b/gtsam/hybrid/HybridValues.h
index 98f862279..89f7bb58a 100644
--- a/gtsam/hybrid/HybridValues.h
+++ b/gtsam/hybrid/HybridValues.h
@@ -53,8 +53,8 @@ class GTSAM_EXPORT HybridValues {
   void print(const std::string& s = "HybridValues",
              const KeyFormatter& keyFormatter = DefaultKeyFormatter) const{
     std::cout << s << ": \n";
-    discrete.print("  Discrete", keyFormatter);
-    continuous.print("  Continuous", keyFormatter);
+    discrete.print("  Discrete", keyFormatter); // print discrete components
+    continuous.print("  Continuous", keyFormatter); //print continuous components
   };
 
   // equals required by Testable for unit testing