Understanding the reference allusion makes often requires knowledge of the culture from which it originates. The book made an allusion to a famous Shakespearean play that not everyone understood.
Pro Tip 2/3
Subtlety Key
An allusion is usually subtle, so it does not explicitly mention the thing it refers to. The song’s lyrics contained an allusion to a historic event without naming it.
Pro Tip 3/3
Recognition Challenge
Detecting an allusion may be challenging and can be missed if you're not familiar with the subject. I missed the allusion to the myth because I hadn't read it yet.