diff --git a/cpp/FactorGraph-inl.h b/cpp/FactorGraph-inl.h
index 724296eac..34aa82754 100644
--- a/cpp/FactorGraph-inl.h
+++ b/cpp/FactorGraph-inl.h
@@ -64,8 +64,8 @@ size_t FactorGraph<Factor>::nrFactors() const {
 /* ************************************************************************* */
 template<class Factor>
 void FactorGraph<Factor>::push_back(shared_factor factor) {
-
 	factors_.push_back(factor);                  // add the actual factor
+	if (factor==NULL) return;
 
 	int i = factors_.size() - 1;                 // index of factor
 	list<string> keys = factor->keys();          // get keys for factor
@@ -157,6 +157,15 @@ Ordering FactorGraph<Factor>::getOrdering() const {
 		return colamd(n_col, n_row, nrNonZeros, columns);
 }
 
+/* ************************************************************************* */
+/** O(1)                                                                     */
+/* ************************************************************************* */
+template<class Factor>
+list<int> FactorGraph<Factor>::factors(const string& key) const {
+	Indices::const_iterator it = indices_.find(key);
+	return it->second;
+}
+
 /* ************************************************************************* */
 /** find all non-NULL factors for a variable, then set factors to NULL       */
 /* ************************************************************************* */
diff --git a/cpp/FactorGraph.h b/cpp/FactorGraph.h
index 77b94e6b3..e39fe1448 100644
--- a/cpp/FactorGraph.h
+++ b/cpp/FactorGraph.h
@@ -82,6 +82,12 @@ namespace gtsam {
 		 */
 		Ordering getOrdering() const;
 
+    /**
+     * Return indices for all factors that involve the given node
+     * @param key the key for the given node
+     */
+    std::list<int> factors(const std::string& key) const;
+
     /**
      * find all the factors that involve the given node and remove them
      * from the factor graph
diff --git a/cpp/LinearFactorGraph.cpp b/cpp/LinearFactorGraph.cpp
index 63052716b..2e4d9147b 100644
--- a/cpp/LinearFactorGraph.cpp
+++ b/cpp/LinearFactorGraph.cpp
@@ -47,14 +47,6 @@ set<string> LinearFactorGraph::find_separator(const string& key) const
 	return separator;
 }
 
-/* ************************************************************************* */
-/** O(1)                                                                     */
-/* ************************************************************************* */
-list<int> LinearFactorGraph::factors(const string& key) const {
-	Indices::const_iterator it = indices_.find(key);
-	return it->second;
-}
-
 /* ************************************************************************* */
 /* find factors and remove them from the factor graph: O(n)                  */
 /* ************************************************************************* */ 
diff --git a/cpp/LinearFactorGraph.h b/cpp/LinearFactorGraph.h
index 1ce89df55..e3e7668c2 100644
--- a/cpp/LinearFactorGraph.h
+++ b/cpp/LinearFactorGraph.h
@@ -67,12 +67,6 @@ namespace gtsam {
      */
     std::set<std::string> find_separator(const std::string& key) const;
 
-    /**
-     * Return indices for all factors that involve the given node
-     * @param key the key for the given node
-     */
-    std::list<int> factors(const std::string& key) const;
-
     /**
      * extract and combine all the factors that involve a given node
      * NOTE: the combined factor will be depends on a system-dependent
diff --git a/cpp/testSymbolicBayesChain.cpp b/cpp/testSymbolicBayesChain.cpp
index 8527e319d..334655176 100644
--- a/cpp/testSymbolicBayesChain.cpp
+++ b/cpp/testSymbolicBayesChain.cpp
@@ -72,7 +72,7 @@ using namespace std;
 using namespace gtsam;
 
 /* ************************************************************************* */
-TEST( SymbolicBayesChain, symbolicFactorGraph )
+TEST( SymbolicFactorGraph, symbolicFactorGraph )
 {
 	// construct expected symbolic graph
 	SymbolicFactorGraph expected;
@@ -98,8 +98,46 @@ TEST( SymbolicBayesChain, symbolicFactorGraph )
 	SymbolicFactorGraph actual(factorGraph);
 
 	CHECK(assert_equal(expected, actual));
+}
 
-	//symbolicGraph.find_factors_and_remove("x");
+/* ************************************************************************* */
+TEST( SymbolicFactorGraph, find_factors_and_remove )
+{
+	// construct it from the factor graph graph
+	LinearFactorGraph factorGraph = createLinearFactorGraph();
+	SymbolicFactorGraph actual(factorGraph);
+  SymbolicFactor::shared_ptr f1 = actual[0];
+  SymbolicFactor::shared_ptr f3 = actual[2];
+	actual.find_factors_and_remove("x2");
+
+	// construct expected graph after find_factors_and_remove
+	SymbolicFactorGraph expected;
+	SymbolicFactor::shared_ptr null;
+	expected.push_back(f1);
+	expected.push_back(null);
+	expected.push_back(f3);
+	expected.push_back(null);
+
+	CHECK(assert_equal(expected, actual));
+}
+/* ************************************************************************* */
+TEST( SymbolicFactorGraph, factor_lookup)
+{
+	// create a test graph
+	LinearFactorGraph factorGraph = createLinearFactorGraph();
+	SymbolicFactorGraph fg(factorGraph);
+
+	// ask for all factor indices connected to x1
+	list<int> x1_factors = fg.factors("x1");
+	int x1_indices[] = { 0, 1, 2 };
+	list<int> x1_expected(x1_indices, x1_indices + 3);
+	CHECK(x1_factors==x1_expected);
+
+	// ask for all factor indices connected to x2
+	list<int> x2_factors = fg.factors("x2");
+	int x2_indices[] = { 1, 3 };
+	list<int> x2_expected(x2_indices, x2_indices + 2);
+	CHECK(x2_factors==x2_expected);
 }
 
 /* ************************************************************************* */