No CrossRef data available.
Published online by Cambridge University Press: 01 August 2016
Many problems in topology are easy to state, but some are extremely difficult to solve. And even if they are easy, they may have surprising solutions. For example, take a tyre inner tube, that is, a toroidal surface with a hole (for the valve!). Can one turn it inside out? The answer is ‘yes’ but if one actually carries out this procedure the result is entirely unexpected.