i found this great article through google for my research paper topic on autism but im having trouble citing
That is a tricky one, but I am pretty sure that is an electronic book. The length and publishing information lead me to that and when I Google searched the title, results that appeared referred to it as a book. As such, you would cite it as an electronic book modeled after this example below, taken from the OWL at Purdue. (The 'n.d.' in the example stands for 'no date' so your citation would have 200o in parentheses, the date on the book you are using):
Electronic books may include books found on personal websites, databases, or even in audio form. Use the following format if the book you are using is only provided in a digital format or is difficult to find in print. If the work is not directly available online or must be purchased, use "Available from," rather than "Retrieved from," and point readers to where they can find it. For books available in print form and electronic form, include the publish date in parentheses after the author's name. For refernces to e-book editions, be sure to include the type and version of e-book you are references (e.g., "[Kindle DX version]"). If DOIs are available, provide them at the end of the reference.
De Huff, E. W. (n.d.). Taytay’s tales: Traditional Pueblo Indian tales. Retrieved from http://digital.library.upenn.edu/women/dehuff/taytay/taytay.html
Davis, J. (n.d.). Familiar birdsongs of the Northwest. Available from http://www.powells.com/cgi-bin/biblio?inkey=1-9780931686108-0
Also, the link to this page from the OWL at Purdue is here: http://owl.english.purdue.edu/owl/resource/560/10/