diff --git a/gtsam/nonlinear/Expression-inl.h b/gtsam/nonlinear/Expression-inl.h
index 9c69cf0f7..15ef269f2 100644
--- a/gtsam/nonlinear/Expression-inl.h
+++ b/gtsam/nonlinear/Expression-inl.h
@@ -232,4 +232,33 @@ typename Expression<T>::KeysAndDims Expression<T>::keysAndDims() const {
   return pair;
 }
 
+// http://stackoverflow.com/questions/16260445/boost-bind-to-operator
+template<class T>
+struct apply_compose {
+  typedef T result_type;
+  static const int Dim = traits<T>::dimension;
+  T operator()(const T& x, const T& y, OptionalJacobian<Dim, Dim> H1 =
+      boost::none, OptionalJacobian<Dim, Dim> H2 = boost::none) const {
+    return x.compose(y, H1, H2);
+  }
+};
+
+/// Construct a product expression, assumes T::compose(T) -> T
+template<typename T>
+Expression<T> operator*(const Expression<T>& expression1,
+    const Expression<T>& expression2) {
+  return Expression<T>(boost::bind(apply_compose<T>(), _1, _2, _3, _4),
+      expression1, expression2);
+}
+
+/// Construct an array of leaves
+template<typename T>
+std::vector<Expression<T> > createUnknowns(size_t n, char c, size_t start) {
+  std::vector<Expression<T> > unknowns;
+  unknowns.reserve(n);
+  for (size_t i = start; i < start + n; i++)
+    unknowns.push_back(Expression<T>(c, i));
+  return unknowns;
+}
+
 } // namespace gtsam
diff --git a/gtsam/nonlinear/Expression.h b/gtsam/nonlinear/Expression.h
index 1ea9e7f49..f81a17c96 100644
--- a/gtsam/nonlinear/Expression.h
+++ b/gtsam/nonlinear/Expression.h
@@ -185,34 +185,21 @@ private:
   friend class ::ExpressionFactorShallowTest;
 };
 
-// http://stackoverflow.com/questions/16260445/boost-bind-to-operator
-template<class T>
-struct apply_compose {
-  typedef T result_type;
-  static const int Dim = traits<T>::dimension;
-  T operator()(const T& x, const T& y, OptionalJacobian<Dim, Dim> H1 =
-      boost::none, OptionalJacobian<Dim, Dim> H2 = boost::none) const {
-    return x.compose(y, H1, H2);
-  }
-};
-
-/// Construct a product expression, assumes T::compose(T) -> T
+/**
+ *  Construct a product expression, assumes T::compose(T) -> T
+ *  Example:
+ *    Expression<Point2> a(0), b(1), c = a*b;
+ */
 template<typename T>
-Expression<T> operator*(const Expression<T>& expression1,
-    const Expression<T>& expression2) {
-  return Expression<T>(boost::bind(apply_compose<T>(), _1, _2, _3, _4),
-      expression1, expression2);
-}
+Expression<T> operator*(const Expression<T>& e1, const Expression<T>& e2);
 
-/// Construct an array of leaves
+/**
+ *  Construct an array of unknown expressions with successive symbol keys
+ *  Example:
+ *    createUnknowns<Pose2>(3,'x') creates unknown expressions for x0,x1,x2
+ */
 template<typename T>
-std::vector<Expression<T> > createUnknowns(size_t n, char c, size_t start = 0) {
-  std::vector<Expression<T> > unknowns;
-  unknowns.reserve(n);
-  for (size_t i = start; i < start + n; i++)
-    unknowns.push_back(Expression<T>(c, i));
-  return unknowns;
-}
+std::vector<Expression<T> > createUnknowns(size_t n, char c, size_t start = 0);
 
 } // namespace gtsam