Citing usually has multiple functions: 1. You use the authority of the source you cite. (If a well-respected researcher has made the point, I may be more likel

Citing usually has multiple functions: 1. You use the authority of the source you cite. (If a well-respected researcher has made the point, I may be more likely to assume it's sensible than if it just came to your mind). This is why citing Wikipedia or single newspaper articles or popular science books may be a less-than-good idea. 2. You point the reader to someone who has invented/first described a certain phenomenon (i.e., recognition of achievement). It's debatable whether that is relevant at an undergraduate level, but it's probably not a bad idea. (Encyclopedias and textbooks are clearly bad on this criterion). 3. You point the reader to a place where he finds more extensive material on the topic. Many encyclopedias do not cite their sources, which makes them less-than-useful on this account. Note the conflict between 2. and 3.: If Someone Else published a cryptic paper in the 50s about something, yet no one understands that one until they've read the excellent overview paper by A. Random Researcher, 2. would say you should cite the Else paper from the 50s, whereas for 3. it may be better to cite Researcher's more recent paper.