Who is graham Greene from Confessions of an Economic Hit Man and what is their importance?

Graham Greene is author of The Power and the Glory, Our Man in Havana, and an article titled The Country with Five Frontiers about how the U.S. might bribe Panama's military chiefs to sabotage treaty negotiations of the Panama Canal. He was close to President Torrijos and was writing a book about Panama. He encouraged John to write a book himself, a coincidence that changed John's life.