The intellectual precursor of Dr Kleinberg's method is the citation index, long used in the academic world.

ECONOMIST: Hits and misses

China has also seen its share of global scientific output, as measured in scientific publications listed in the Science Citation Index (SCI), double between 2002 and 2008 from 5.2% to 10.6%, placing it second only to the USA in numerical terms.

UNESCO: MEDIA SERVICES