History of the Peloponnesian War
Thucydides
Thucydides. The history of the Peloponnesian War, Volume 1-2. Dale, Henry, translator. London: Heinemann and Henry G. Bohn, 1851-1852.
On his arrival then at this time in the countries Thrace-ward, the Athenians, when they heard it, declared war against Perdiccas, thinking that he was the cause of his march thither; and kept a closer watch over their allies in that quarter.