Found in articles
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Matthias (eds.). Handbook of Comparative and Historical Indo-European Linguistics (به انگلیسی). Vol. 3. Walter de Gruyter. p. 1843. ISBN 978-3-11-054243-1.
Scarecrow Press. p. 33. ISBN 978-0-8108-4237-3. Retrieved October 25, 2015. Nessa Wolfson; Joan Manes (1985). Language of Inequality. Walter de Gruyter. p. 176
Ages to the present]. de Gruyter Studienbuch (به آلمانی). Vol. Band III: 19. und 20. Jahrhundert. Berlin; New York: de Gruyter. ISBN 978-3-11-016426-8
(1998), Systems: new paradigms for the human sciences (به انگلیسی), Walter de Gruyter, p. 231 Derek K. Hitchins (2007), "Optimize Solution System Design", Systems