Halliday & Matthiessen (2014: 516):
As with nexuses projecting locutions, nexuses projecting ideas consist of a phenomenon — the projecting clause — and a metaphenomenon — the ‘content’ of the projecting clause; for example, in some experts believe that people someday will have their unique genetic code on smart cards ... , the phenomenon is some experts believe and the metaphenomenon is that people someday will have their unique genetic code on smart cards ... .