This site is not particullarly reliable, it is more of a third party website made by someone who wants to provide information on Alexander the Great. What it useful about it is it's bibliography, it provides a lot of information on the sources on Alexander. I would recomend using this to find out who the sources are, and then try to research further into them.
This is the Campaigns of Alexander, by Arrian, an ancient source on Alexander, but a secondary source because he was a Greek who lived during Roman times.
Provides a lot of information on Pericles, but it is hard to access if you do not have an account for the website. What is more useful is the information on Thucydides' relationship with Pericles and his reliability as a souce on Pericles in the second paragraph.