1. Lubker BB. Epidemiology: An essential science for speech-language pathology and audiology.Journal of Communication Disorders. 1997; 30( 4): 251-267.##
2. Antoniadis A, Lubker BB. Epidemiology as an essential tool for establishing prevention programs and evaluating their impact and outcome .Journal of Communication Disorders.1997; 30( 4): 269-284.##
3. Paul R.Language disorders: from infancy through adolescence.assessment and intervention .2nded, St. Louis: Mosby; 2001:108.##
4. Zheng XY, Zhang L, Chen G, Pei LJ, Song XM. Prevalence of visual, hearing, speech, physical, intellectual and mental disabilities in China, 2006.Zhonghua Liu Xing Bing XueZaZhi. 2008;29(7):634-8.##
5. Karbasi SA, Fallah R, Golestan M. The prevalence of speech disorder in primary school students in Yazd-Iran.Acta Med Iran. 2011;49(1):33-7.##
6. Ward D. Stuttering and Cluttering :Frameworks for understandingand treatment. New York: Lippincott Williams & Wilkins. 2006.##
7. Guitar B. Stuttering : an integrated approach to its nature and treatment. 3rd  ed .Philadelphia: Lippincott Williams & Wilkins, 2006.##
8. Marlyn L. andEiner B. Result of intensive stuttering therapy with adults who stutter. Journal of fluency disorders; 1996:21,315-325.##
9. Mohammadi  H, Nilipour R, Yadegari F, prevalence of stuttering in Kurdish-persian consecutive Biliguals in Iran. Asia pacific  Journal of speech ,language and hearing. 2010; 13(4)##
10. Nikkhoo MR, Pasha Sharifi H.Diagnostic and Statistical Manual of Mental Disorders.Tehran: Shahed University.1996##
11. Garcia de Goulart BN, Chiari BM. Prevalence of speech disorders in schoolchildren and its associated factors. Rev SaudePublica.2007;41(5):726-31.##
    1. Qvarnstr M, Laine T, Jaroma M. prevalence of articulatory disorders of different sounds in a group of finnish first-graders. J. commun.Disord. 24 (1991(, 381-392.##
    2. Milisen, R.The incidence of speech disorders.In L. E. Travis (ed.), Handbookof Speech Pathology and Audiology. New York: Appleton-CenturyCrofts. 1971.##
    3. Sadolahi A, Genabi M, KasbiF,Eftekhari Z, Ghorbani R. prevalence of articulation disorders primary schoolers in the city of Semnan. Journal of Semnanuniversity of medical sciences. 2004; 6(1): 57-62.##
    4. Boone D.R, McfarlaneS,VonbergSh, the voice and voice therapy.7th ed.philadelphia; Allyn & Bacon Communication Sciences and Disorders. 2004.##
    5. Aronson  A.Clinical voice disorders. ThiemeInc: NewYork;2000.##
    6. Johnson AF, Jacobson BH. Medical speech-language pathology: a practitioner's guide.  New York  :Thieme ;1998: 613.##
    7. Sonnander K, Claesson M. Classification, prevalence, prevention and rehabilitation of intellectual disability: an overview of research in the People's Republic of China.J Intellect Disabil Res. 1997;41 ( Pt 2):180-92.##
    8. GenetA.H,The birth prevalence of PKU in populations of European, South Asian andsub-Saharan African ancestry living in South East England.2008;72(Pt 1):65-71 .##
    9. Worley JA, Matson JL, Sipes M and Kozlowski AM. Prevalence of autism spectrum disorders in toddlers receiving early intervention services.Research in Autism Spectrum Disorders. 2011;5 : 920–925.##
    10. RiceJoyceC,Baio N.J, Pettygrove S, Lee L, Braun K.V, Doernberg N, Craig C, Meaney, Jane Charles J, King A, MancillaM.K,Mervis C, Carpenter L.Yeargin-Allsopp M, Changes in autism spectrum disorder prevalence in 4 areasof the United States Disability and Health Journal 2010; 3 : 186-201##
    11. Burd L, Fisher W, and Kerbashian J.A Prevalence Study of Pervasive Developmental Disorders in North Dakota.Journal of the American Academy of Child & Adolescent Psychiatry.1987; 26(5): 700-703.##
    12. Parving A. Hearing screening – aspects of epidemiology and identification ofhearing impaired children.International Journal ofPediatricOtorhinolaryngology.1999 ; 49(1): 287-292##
    13. -PsarommatisM,Goritsa E, DouniadakisD,Tsakanikos M, Kontrogianni A, NikolaosA. Hearing loss in speech-language delayed childrenIoannispostolopoulosInternationalJournal of Pediatric Otorhinolaryngology .2001 ;58:205–210##
    14. Hajloo N, Ansari S, prevalence and causes of hearing handicap in Ardabil provinces western Iran.Audiology. 2011; 20(1):116-127.##
    15. Baradaranfar MH, Millasadeghi A, Atighe chi S, HadadzadeH,Akbari H. prevalence of hearing disorders among the 3-6 years old children of kindergartens of Yazd city. Journal of shaheedSadoughiuniversity. 2009, 16(5): 20-25.##
    16. Luan C, Liu M.Comparison of prevalence of physical disabilities in year 2006 and 1987, inChina.Zhonghua Liu Xing Bing XueZaZhi.2008;29(7):639-42.##
    17. Paul TJ, Desai P, ThorburnMJ.The prevalence of childhood disability and related medical diagnoses in Clarendon, Jamaica.West Indian Med J. 1992;41(1):8-11.##
    18. Farrag AF, El-Behary AA, Kandil MR. Prevalence of specific reading disability in Egypt. The Lancet. 1988; 332(8615): 837-839##
    19. Rahimianbougar E, Sadeghi A. prevalence of reading disorder in primary school students. Iranian Journal of psychiatry and clinical psychology. 2007; 12(4(47)):396-402##
    20. Mc Neill MR. clinical management of sensory motor speech disorders.Second Edition. New York:Thieme; 2009.

32.    Damico J.S, Muller N, Ball M.J.The Handbook of Language and SpeechDisorders.Oxford:Blackwell; 2010: 318-319.##