Some e-books are assigned a DOI, which should also be included in your reference if given.
Standard format for citation
DOI available
| Author, A., and Author, B.(date of original publication). Title of e-book: Subtitle. Place of Publication: Publisher. doi:10.XXXX/XXXXXXXX.XX |
No DOI available
| Author, A., and Author, B.(date of original publication). Title of e-book: Subtitle. Place of Publication: Publisher. Retrieved from Source: internet address |
Electronic books
Eckes, T. (2000). The developmental social psychology of gender. Mahwah, NJ: Lawrence Erlbaum. Retrieved from netLibrary: http://www.netlibrary.com
Bass, L., Clements, P., & Kazman, R. (2003). Software architecture in practice (2nd ed.). Reading, MA: Addison Wesley. Retrieved from Safari: http://proquest.safaribooksonline.com/
Chapter from an electronic book
Jones, N. A., & Gagnon, C. M. (2007). The neurophysiology of empathy. In T. F. D. Farrow & P. W. R. Woodruff (Eds.), Empathy in mental illness. Cambridge, England : Cambridge University Press. Retrieved from EBL: http://reader.eblib.com.au
Article from an electronic encyclopaedia
Lai, M. C. C. (1999). Hepatitis delta virus. In A. Granoff & R. Webster (Eds.), Encyclopedia of virology (2nd ed.). San Diego, CA: Academic. 
doi:10.1016/B978-012374410-4.00417-9
Article from an electronic encyclopaedia: No author
Depression (psychology) (2001). In Microsoft Encarta online encyclopedia 2002. Microsoft. Retrieved from http://encarta.ninemsn.com.au
Article from an electronic dictionary: No author
Suffragettes. (2003). In J. Palmowski (Ed.), A dictionary of contemporary world history. Oxford, England: Oxford University Press. Retrieved from Oxford Reference Online.