For the student and scholar, reference can have two meaning. One, a source that you can refer to for answers, and also the source, or reference, that accompanies a book or article. A good encyclopedia article gives you the best of both. Try starting your research with Credo Reference.
Browse a reference work
Mandrake root was well known before Harry Potter & friends had to repot it, or even before John Donne penned “get with child a mandrake root.” Besides reference works giving you solid background information & a list of sources to jumpstart your research, you can explore an idea across disciplines. Learn from The Cambridge World History of Food that the ancients associated mandrake with the witch Circe (of The Odyssey fame) and love potions before it became known as an aphrodisiac. Its berries glow in the first light of dawn and the demon mandragoros dwells with in it ... so relates The Encyclopedia of Witches, Witchcraft, & Wicca and the only safe way to harvest it is to tie your dog to the plant and when the faithful beast tries to follow you home it uproots the plant and dies a horrible death, but the blood sacrifice gives the root the power over demons. In A Dictionary of English Folklore we learn mandrake grows under “gallows and gibbets” and from the Concordance to Shakespeare we can discover every reference the Bard made to mandrake, such as this imploration “would curses kill, as doth the mandrake’s groan” (2 Hen. VI. Iii, 3 224).
This class hops across disciplines. Here are a few places to start with encyclopedias.
One of the basic tricks of research is to build on the work of others. The author of a scholarly work lists the resources she or he used as source material for their book or article. Take advantage of the work they have done and browse the bibliography or reference list or works cited. Think of it as an expert giving you a little personal advice.
Bibliographies can be relatively short, like these six books from the article on James I of England (king & witch hunter!) from The Encyclopedia of Witches, Witchcraft, & Wicca.
Or extensive, like this seventy-five items + bibliography from the article "Harry Potter and Contemporary Magic: Fantasy Literature, Popular Culture, and the Representation of Religion" from the Journal of Contemporary Religion. When you find something of interest it is then a simple matter to find the full-text using SOLAR or a library catalog. And anytime you are unsure, just ask a Librarian for help.