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33- Gairdner, W.H.T: The Phonetics of صلى الله عليه وسلمrabic, "Oxford University Press,1925".

34- Heffner, R.M.S: General Phonetics "The University of Wisconsim Press 1960".

35- Hass, W: Zero in linguisitcs "Studies in Linguistic analysis, special vol. of the Philological Society. 1957, pp. 33-53".

36- Robins, R.H: General Linguistics: صلى الله عليه وسلمn Introductory Suvey Longmans, Green & Co. Ltd. 1964".

37- Wright, W: صلى الله عليه وسلم Grammar of the صلى الله عليه وسلمrabic Language, translated from the German of Caspari, "third ed., Cambridge University Press, 1951".