What is an example of allusion in To Kill a Mockingbird in Chapters 4-8?

An allusion is a figure of
speech that makes a reference to, or representation of, a place, event, literary work,
myth, or work of art, either directly or by implication. There are many found in the
text of To Kill a Mockingbird, and I have provided several examples
from Chapters 4-8.

• CHAPTER 4.  There is an
  allusion to the Rover Boys, a series of books for young readers of the 1930s; Hot
  Steams, a type of ghostly apparition; and the L&N
  Railroad.


• CHAPTER 5.  The World War I Battle of the Marne
  is mentioned as is Confederate cavalry commander General Joe
  Wheeler.


• CHAPTER 8.  The ancient Rosetta Stone is
  referenced in relation to Mr. Avery; the Civil War surrender site of Appomattox is
  mentioned; and another book series, Tom Swift, serves as an
  allusion.