I would recommend going to our history research guide here: http://libguides.uah.edu/hy103 and selecting the Primary Sources tab. Your best bet will probably be the Internet Ancient History Sourcebook. Click on that link and then select Greece from the left hand column and take a look around.
There is a link for Delian League under the Athenian Democracy heading, but it has a 2ND next to it, which means it is a secondary source. One of the other links from this section might be helpful, though.
If you are off campus, you'll need to log in with your UAH credentials (username is your UAH e-mail address before the @ and your campus-wide password).