In some cases reference books tend to be more reliable and probably easier to find and use. If you decide to use a search engine - think about your 'search strategy'. A search on the Web is most likely to succeed if your search can be defined in terms of an uncommon word or phrase - such as a proper name. No search engine is comprehensive - so be prepared to use more than one. Read the help screens to ensure that you are entering your search correctly.
Many search engines give a relevancy rating to search results.
Search engines are developing all the time. Expect them to change.