Thanks to the development of the internet and bibliographic databases, they can now be explored with relative ease. It has been suggested that in order to be comprehensive, we should apply LILACS in our literature search to cover Spanish and Portuguese articles in our systematic Emerging Themes in Epidemiology 2008, 5:20 http://www.ete-online.com/content/5/1/20 reviews [78, 79] . Perhaps it is time to add to our list the Chinese databases and also include Chinese papers.