Sir

Litera scripta manet: 'written words will endure'. But not, it seems, in the case of the e-mail addresses of corresponding authors in the scientific literature.

To investigate the survival rate of author e-mail addresses, I sent an e-mail to the first one hundred corresponding authors of peer-reviewed papers whose addresses were returned in a Google Scholar search for 2007 and 2003. Roughly one out of five messages was undeliverable in 2008 (from 2007: 17%; 2003: 25%), indicating that those e-mail addresses were no longer valid.

E-mail addresses of scientists, particularly those without tenure, are volatile. Researchers leave behind a trail of obsolete e-mail addresses, phone numbers and fax numbers in the printed literature.

Unique digital author identifiers, as proposed in Correspondence (Nature 453, 979; 2008), could be linked to up-to-date e-mail addresses and other contact information. This would increase the traceability of authors, facilitate scientific networking, and even speed up the peer-review process.