Buffer::References const & refs = buffer().references(old_label);
Buffer::References::const_iterator it = refs.begin();
Buffer::References::const_iterator end = refs.end();
for (; it != end; ++it) {
Buffer::References const & refs = buffer().references(old_label);
Buffer::References::const_iterator it = refs.begin();
Buffer::References::const_iterator end = refs.end();
for (; it != end; ++it) {