We retrieved the full-text articles for citations selected for possible inclusion in the systematic review.

If you are seeking additional full-text articles, please visit PubMed Central.

Redalyc has been consolidated as an important repository of knowledge with 550 journals online and more than 116 000 full-text articles.

Launched in 1999, it is a self-contained agricultural research library with full-text articles and graphics of over 200 major journals.

Footnotes give many links to free full-text articles arguing both sides.

A digital archive of full-text articles from over 130 life sciences journals.

This database also provides links to the Web sites of over 1,800 journals, allowing users to view full-text articles.

The journal offers access to full-text articles published from 2001.

How can I get the full-text article?

It also includes links to many full-text articles at journal Web sites and other related Web resources.