docs: mention the different types of exact specifications and pep440

docs/dependency-specification.md

@@ -79,11 +79,15 @@ Multiple version requirements can also be separated with a comma, e.g. `>= 1.2,
 
 
 You can specify the exact version of a package.
 You can specify the exact version of a package.
 
 
-`==1.2.3` is an example of an exact version specification.
+`1.2.3` is an example of an exact version specification.
 
 
 This will tell Poetry to install this version and this version only.
 This will tell Poetry to install this version and this version only.
 If other dependencies require a different version, the solver will ultimately fail and abort any install or update procedures.
 If other dependencies require a different version, the solver will ultimately fail and abort any install or update procedures.
 
 
+Exact versions can also be specified with `==` according to [PEP 440](https://peps.python.org/pep-0440/).
+
+`==1.2.3` is an example of this.
+
 ### Using the `@` operator
 ### Using the `@` operator
 
 
 When adding dependencies via `poetry add`, you can use the `@` operator.
 When adding dependencies via `poetry add`, you can use the `@` operator.