De Guilleuma investigated a reference in a book published in 1609 by the Italian Girolamo Sirtori.

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These "known unknowns" he dubbed "grey swans", in a reference to Nicholas Nassim Taleb's book "The Black Swan", about the nature of unpredictability.

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But it is an excellent reference book for anyone wanting a better understanding of economic developments in the last millennium.

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L. James's book, you will know that the Grey in question is one of the protagonists rather than a reference to a fashion lexicon.

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Bizarrely, one of Dr Lomborg's critics in Scientific American criticises as an affectation the book's insistence on documenting every statistic and every quotation with a reference to a published source.

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The writer is set to release his memoirs, entitled Joseph Anton - the name he used while in hiding, and a reference to his favourite authors Conrad and Chekhov - which tell of how he was forced underground in 1989 over his book.

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