Although important as a pioneer of historical Chinese linguistics, Karlgren's original findings have been surpassed. Today the phonological systems proposed by Karlgren have largely been superseded, as their weaknesses are obvious: "Karlgren saw himself as reconstructing phonetics, not phonology, and paid little attention to phonological structure. As a result, the systems he reconstructed often lack the symmetry and pattern which are in the phonological systems of natural languages." Nevertheless, Karlgren's groundbreaking works laid the foundation of modern Chinese historical linguistics and many of his works are still used as works of reference.