-template<> int convert<int>(std::string const s);
-template<> int convert<int>(docstring const s);
-template<> unsigned int convert<unsigned int>(std::string const s);
-template<> unsigned long convert<unsigned long>(std::string const s);
-template<> double convert<double>(std::string const s);
+template<> int convert<int>(std::string const & s);
+template<> int convert<int>(docstring const & s);
+template<> unsigned int convert<unsigned int>(std::string const & s);
+template<> unsigned long convert<unsigned long>(std::string const & s);
+template<> double convert<double>(std::string const & s);