|  | ANSI Common Lisp  13 Characters  13.1 Character Concepts  13.1.4 Character Categories 13.1.4.3   Characters With CaseThe characters with case are 
a subset of the alphabetic1 characters.
A character with case has the property of being either
uppercase or lowercase.
Every character with case is in one-to-one correspondence
with some other character with the opposite case.13.1.4.3.1  Uppercase Characters
13.1.4.3.2  Lowercase Characters
 13.1.4.3.3  Corresponding Characters in the Other Case
 13.1.4.3.4  Case of Implementation-Defined Characters
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