Ironically, you missed all those that refer to 'purple coneflower'. Be aware of how the search engines operate. Only a few cover the Web exhaustively, in terms of the URL's they tag, and how thorough their indexing of the pages and document is. Using only one search engine does not guarantee that all the information existent on the WEB, on say, visualization techniques and cancer, will be returned. Conversely, a search engine might return thousands of irrelevant documents, as we saw by the previous examples.
Search engines operate in two prevailing areas.
Oncolink's site-specific search engine represents the less conspicuous, second general area of search engines, those of individual institutions or groups. These search engines limit themselves to the content particular to their Web site, the site being so large that it needs its own search engine and interface to find information within the site. Some search engines have developed multi field boxes that accommodate more than one term, and other search capabilities. While the goals of search engines are the same, to retrieve information for the user- their methods are often somewhat different, so affecting what you put in the field. The advanced search features listed below impact on what you enter in the field, and what is returned to you.