Context:

Referenced as 'his novel' by Robert Graves when discussing the falling out between Justinian and Belisarius - 'their falling out that Robert Graves writes about in his novel'

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Referenced multiple times as Procopius's scandalous account of Justinian and Theodora, containing the famous passages about Theodora's past and criticisms of Justinian as a demonic figure

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Explicitly mentioned as one of Procopius's works - 'he also writes a book about the monuments that Justinian raises. With a brilliant title, On Buildings.'

Context:

Referenced as Procopius's historical account of the Vandal War and conquest of Italy, described as more respectful of Justinian than the Secret History