I'm doing an essay on why so few of the Roman emperors of the third and fourth centuries died natural deaths. Would anyone be able to point me towards some primary sources from this period? Any recommendations for secondary sources would be welcome too.
Ammianus Marcellinus was a soldier and historian who wrote about the mid-fourth century, especially during the reign of Julian the Apostate. He actually witnessed many of the events he wrote about, and is a very interesting writer to boot.
Here's a link to his work: http://www.gutenberg.org/files/28587/28587-h/28587-h.htm