Sam can also tell, with a bit of experience, by browsing through some of the periodical titles listed. In this case, he won't want to choose Readers Guide which will contain citations to popular magazine articles. Find out what time period is included. For Sam's hazardous waste topic, he needs both current and older information. An index that offers full text may be useful here for current information, but won't contain articles with older information.
Government information is very often accessible via the Web.
This is a good opportunity for Sam to contact a librarian and ask for pointers to government statistical information sites. It will be an easy email question if he explains what his topic is and what kind of statistics he thinks he'll need to support his emerging idea. The librarian can send him URLs to sites already identified as reliable. This in-depth research paper required a circular approach to research. Sam returned to the library catalog, resource people, the Web and books and journals in the library several times before he was ready to write.