There is little empirical evidence as to the value of using general internet search engines such as Google to identify potential studies (Eysenbach 2001). Searching research funders’ and device manufacturers’ web sites might be fruitful. Searching pharmaceutical industry web sites may be useful, in particular their trials registers, covered in Section 6.2.3.3. If internet searches are conducted, it is recommended that review authors should file a print copy or save locally an electronic copy of details of information about any possibly relevant study found on the internet, rather than simply ‘book-marking’ the site, in case the record of the trial is removed or altered at a later stage. It is important to keep a record of the date the web site was accessed for citation purposes.