(link:) Use to find backlinks of any webpage, even using their anchor text. Example: link:http://www.salud.es/diabetes diabetes
(linkdomain:) look for the backlinks of any domain. Example: link:http://www.salud.es/salud
(originurlextension:) look only for files with a specific extension. Example: originurlextension:pdf
(region:) Use it for locating websites in a specific continent. Example: region:europe. Other possible values: europe, africa, asia, centralamerica, downunder, mediterranean, mideast, northamerica, southamerica, southeastasia.
(url:) Use it to know if a specific website has been indexed by Yahoo! Example: url:http://www.salud.es