"The latest research, published in the Proceedings of the National Academy of Sciences (PNAS), found that a wave precisely targeted through the inner core behaved differently depending on which part of the core it travelled through." (BBC, 2002)
BBC (2002) "Quakes Reveal 'Core within a Core'". [online] http://news.bbc.co.uk/2/hi/sci/tech/2290551.stm
