Indisputable Existence of Santa Claus

____________How do you apply game theory to select who should be on your Christmas shopping list ? Can you predict Her Majesty's Christmas Message? Will calculations show Santa is getting steadily thinner - shimmying up and down chimneys for a whole night - or fatter - as he tucks into a mince pie and a glass of sherry in billions of houses across the world?Full of diagrams, sketches and graphs, ...