Other
Literary Devices: Allusion: Examples and Definition
This site defines Allusion and then provides several examples of allusion in literature including Milton's Paradise Lost, Marlowe's Doctor Faustus, Conrad's Heart of Darkness, and Keats's Ode to the Grecian Urn. It also discusses the...
Other
English Grammar Online: Stylistic Devices: Allusion
If you need a brief, clear explanation of allusion and how it works, this is a good place to start.
Washington State University
Washington State University: Allusion/illusion
A brief definition of allusion with examples. Differentiates between the term allusion and the term illusion.