Clarke, D. S. [ca. 2003]. Sign levels : language and its evolutionary antecedents. In Philosophical studies series [Book]. Dordrecht [u.a.]: Kluwer Academic.

CLARKE, David S., 2003. Sign levels : language and its evolutionary antecedents. Dordrecht [u.a.]: Kluwer Academic. Philosophical studies series, 96. ISBN 1402016506.

Clarke, D. S. „Sign levels : language and its evolutionary antecedents“. Philosophical studies series, book, Kluwer Academic, 2003.

Clarke, David S.: Sign levels : language and its evolutionary antecedents, . Philosophical studies series, Dordrecht [u.a.] 2003.

Clarke, D.S. (2003), Sign levels : language and its evolutionary antecedents, Philosophical studies series, Bd. , Kluwer Academic, Dordrecht [u.a.].