Sir

Scientists and whole institutes are frequently judged by the number of citations of their papers in scientific journals, and project funding depends on it. But, as Clint Kelly and Michael Jennions note in Correspondence ('H-index: age and sex make it unreliable' Nature 449, 403; doi:10.1038/449403c 2007), the context and relevance of citations are crucial in reaching this judgement.

Researchers from developing nations often face another problem. In the name of local issues and the national interest, they are required to publish in national journals that rarely find a place among cited journals and have a very limited circulation abroad.

For example, a study of the Thomson Scientific Essential Science Indicators (ESI) during the past five years has found that the National Geophysical Research Institute (NGRI) in Hyderabad, India, scores among the top 1% of institutions publishing in the geosciences. During this period, the NGRI had 2,338 citations of 657 papers (http://www.in-cites.com/institutions/2007menu.html). But if it had not published more than half its publications in national journals — not all of which figure in the ESI database — the NGRI could have been ranked even nearer the top.

In formulating their criteria, publications from institutes and by individuals in local and national journals should also be taken into account: this could be done by assigning some weighted average. The total number of publications in national journals not counted by the ESI would then be considered and weighted in order to arrive at a more appropriate index.