diff --git a/docs/basics.rst b/docs/basics.rst
index 9c222eb4..8a9460e7 100644
--- a/docs/basics.rst
+++ b/docs/basics.rst
@@ -188,6 +188,7 @@ To tell pipenv to install a specific version of a library, the usage is simple::
 
 This will update your ``Pipfile`` to reflect this requirement, automatically.
 
+For other version specifiers, see `PEP-440 <(https://www.python.org/dev/peps/pep-0440/#version-specifiers>`.
 
 ☤ Specifying Versions of Python
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