-void warning_pimpl(string const & title, string const & warning);
-void error_pimpl(string const & title, string const & warning);
-void information_pimpl(string const & title, string const & warning);
+void warning_pimpl(std::string const & title, std::string const & warning);
+void error_pimpl(std::string const & title, std::string const & warning);
+void information_pimpl(std::string const & title, std::string const & warning);