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Referenced as a book written in 1930 that makes jokes about British historical knowledge, specifically mentioning that 55 BC and 1066 are the only two dates in the book

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Mentioned as a childhood book that presented the Roman conquest of Britain as generally a good thing, introducing hot baths, wine, and straight roads

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Caesar's account of the Gallic War is quoted at the beginning and referenced throughout as the primary source for the Roman invasion of Britain

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Referenced as Caesar's biographer who reported the story about Caesar seeing Alexander the Great's statue in Cadiz and having a dream about his mother, written about 180 years after the events

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Explicitly mentioned as 'his book On the Ocean, which hasn't survived, but is quoted a lot' - an ancient Greek text describing Britain, Ireland, and Ultima Thule from around 320 BC

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Referenced as a comic book series that depicts Vercingetorix throwing his armour down at Caesar's feet, parodying a famous historical image