Lyle Campbell & Mauricio J. Mixco: A Glossary of Historical Linguistics. Edinburgh University Press, 2007, ISBN 978-0-7486-2378-5, S.7, 90f. (englisch, academia.edu): “most specialists […] no longer believe that the […] Altaic groups […] are related. […] Korean is often said to belong with the Altaic hypothesis, often also with Japanese, though this is not widely supported”
