diff --git a/.github/workflows/docs.yaml.bkp b/.github/workflows/docs.yaml.bkp
index 120c5dbd..ac5211ea 100644
--- a/.github/workflows/docs.yaml.bkp
+++ b/.github/workflows/docs.yaml.bkp
@@ -27,7 +27,7 @@ jobs:
           pip install .
           pip install -r package/requirements.mkdocs.txt
       - name: Build documentation
-        run: python src/export docs
+        run: python package/export docs
       # set up Pages
       - name: Set up Pages
         uses: actions/configure-pages@v3
diff --git a/.github/workflows/package.yaml b/.github/workflows/package.yaml
index 041f98fc..aa82a7b9 100644
--- a/.github/workflows/package.yaml
+++ b/.github/workflows/package.yaml
@@ -34,7 +34,7 @@ jobs:
       - name: Build package
         run: |
           . ./.venv/bin/activate
-          python src/export package
+          python package/export pkg
           deactivate
       # upload package as artifact
       - name: Upload artifact
diff --git a/MANIFEST.in b/MANIFEST.in
index a5a305ed..b68967ac 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -7,7 +7,6 @@ include .gitignore
 # global-include
 
 recursive-include tests *
-recursive-include src/export *
 
 # graft
 
@@ -16,6 +15,7 @@ recursive-include src/export *
 # global-exclude
 
 recursive-exclude docs *.rst
+recursive-exclude docs/references *.md
 
 prune docs/_build
 prune **/__pycache__
diff --git a/mkdocs.yaml b/mkdocs.yaml
index b25bc374..252f2423 100644
--- a/mkdocs.yaml
+++ b/mkdocs.yaml
@@ -64,21 +64,3 @@ copyright: Copyright © 2013 - 2024 Konsta Vesterinen
 
 nav:
   - Home: index.md
-  - API:
-      - references/between.md
-      - references/btc_address.md
-      - references/card.md
-      - references/country_code.md
-      - references/domain.md
-      - references/email.md
-      - references/hashes.md
-      - references/hostname.md
-      - references/i18n.md
-      - references/iban.md
-      - references/ip_address.md
-      - references/length.md
-      - references/mac_address.md
-      - references/slug.md
-      - references/url.md
-      - references/utils.md
-      - references/uuid.md
diff --git a/src/export/__init__.py b/package/export/__init__.py
similarity index 100%
rename from src/export/__init__.py
rename to package/export/__init__.py
diff --git a/src/export/__main__.py b/package/export/__main__.py
similarity index 95%
rename from src/export/__main__.py
rename to package/export/__main__.py
index dc501be2..ffe89bb3 100644
--- a/src/export/__main__.py
+++ b/package/export/__main__.py
@@ -40,13 +40,13 @@ def _parse_package(source: Path):
 
 def _generate_reference(source: Path, destination: Path, ext: str):
     """Generate reference."""
-    nav_items: Dict[str, List[str]] = {"Code Reference": []}
+    nav_items: Dict[str, List[str]] = {"API": []}
     # generate reference content
     for module_name, aliases in _parse_package(source):
         for alias in aliases:
             _write_ref_content(destination / f"{module_name}.{ext}", module_name, alias.name)
         if ext == "md":
-            nav_items["Code Reference"].append(f"references/{module_name}.md")
+            nav_items["API"].append(f"references/{module_name}.md")
     return nav_items
 
 
@@ -65,6 +65,9 @@ def _update_mkdocs_config(source: Path, destination: Path, nav_items: Dict[str,
 
 def _gen_md_docs(source: Path, refs_path: Path):
     """Generate Markdown docs."""
+    # remove existing markdown files
+    for md_files in (source / "docs/references").glob("*.md"):
+        md_files.unlink()
     nav_items = _generate_reference(source / "src/validators/__init__.py", refs_path, "md")
     # backup mkdocs config
     _update_mkdocs_config(source / "mkdocs.yaml", source / "mkdocs.bak.yaml", nav_items)
@@ -166,7 +169,7 @@ def package(source: Path):
     if len(argv) != 2:
         quit(exit_code)
 
-    if argv[1] == "package":
+    if argv[1] == "pkg":
         exit_code = package(project_root)
     if argv[1] == "docs":
         exit_code = generate_documentation(
diff --git a/package/roll.ps1 b/package/roll.ps1
index 4441807c..c565b83a 100644
--- a/package/roll.ps1
+++ b/package/roll.ps1
@@ -46,7 +46,7 @@ if ($IsLinux || $IsMacOS) {
 . $venv_dir\$bin_path\Activate.ps1
 
 # Run export script
-python src/export package
+python package/export pkg
 
 # Deactivate virtual environment
 deactivate
diff --git a/package/roll.sh b/package/roll.sh
index 37ed0830..5287a162 100755
--- a/package/roll.sh
+++ b/package/roll.sh
@@ -40,7 +40,7 @@ $venv_dir/bin/pip install build
 . $venv_dir/bin/activate
 
 # Run export script
-python src/export package
+python package/export pkg
 
 # Deactivate virtual environment
 deactivate
diff --git a/src/validators/between.py b/src/validators/between.py
index 2fc3a0c9..0cd79d46 100644
--- a/src/validators/between.py
+++ b/src/validators/between.py
@@ -57,42 +57,25 @@ def between(
             If `value` is not in between the given conditions.
 
     Raises:
-        ValueError: If both `min_val` and `max_val` are `None`,
-            or if `min_val` is greater than `max_val`.
-        TypeError: If there's a type mismatch before comparison.
+        (ValueError): If `min_val` is greater than `max_val`.
+        (TypeError): If there's a type mismatch during comparison.
 
     Note:
         - `PossibleValueTypes` = `TypeVar("PossibleValueTypes", int, float, str, datetime)`
-        - Either one of `min_val` or `max_val` must be provided.
-
-    > *New in version 0.2.0*.
+        - If neither `min_val` nor `max_val` is provided, result will always be `True`.
     """
     if value is None:
         return False
 
-    if min_val is max_val is None:
-        raise ValueError("At least one of either `min_val` or `max_val` must be specified")
-
     if max_val is None:
         max_val = AbsMax()
     if min_val is None:
         min_val = AbsMin()
 
-    if isinstance(min_val, AbsMin):
-        if type(value) is type(max_val):
-            return min_val <= value <= max_val
-        raise TypeError("`value` and `max_val` must be of same type")
-
-    if isinstance(max_val, AbsMax):
-        if type(value) is type(min_val):
-            return min_val <= value <= max_val
-        raise TypeError("`value` and `min_val` must be of same type")
-
-    if type(min_val) is type(max_val):
+    try:
         if min_val > max_val:
-            raise ValueError("`min_val` cannot be more than `max_val`")
-        if type(value) is type(min_val):  # or is type(max_val)
-            return min_val <= value <= max_val
-        raise TypeError("`value` and (`min_val` or `max_val`) must be of same type")
+            raise ValueError("`min_val` cannot be greater than `max_val`")
+    except TypeError as err:
+        raise TypeError("Comparison type mismatch") from err
 
-    raise TypeError("`value` and `min_val` and `max_val` must be of same type")
+    return min_val <= value <= max_val
diff --git a/src/validators/length.py b/src/validators/length.py
index 92a274d3..be60d06e 100644
--- a/src/validators/length.py
+++ b/src/validators/length.py
@@ -1,12 +1,15 @@
 """Length."""
 
+# standard
+from typing import Union
+
 # local
 from .between import between
 from .utils import validator
 
 
 @validator
-def length(value: str, /, *, min_val: int = 0, max_val: int = 0):
+def length(value: str, /, *, min_val: Union[int, None] = None, max_val: Union[int, None] = None):
     """Return whether or not the length of given string is within a specified range.
 
     Examples:
@@ -33,6 +36,12 @@ def length(value: str, /, *, min_val: int = 0, max_val: int = 0):
         (ValidationError):
             If `len(value)` is not in between the given conditions.
 
-    > *New in version 0.2.0*.
+    Raises:
+        (ValueError): If either `min_val` or `max_val` is negative.
     """
-    return between(len(value), min_val=min_val, max_val=max_val) if value else False
+    if min_val is not None and min_val < 0:
+        raise ValueError("Length cannot be negative. `min_val` is less than zero.")
+    if max_val is not None and max_val < 0:
+        raise ValueError("Length cannot be negative. `max_val` is less than zero.")
+
+    return bool(between(len(value), min_val=min_val, max_val=max_val))
diff --git a/tests/test_between.py b/tests/test_between.py
index 6b1ccd72..bdb71551 100644
--- a/tests/test_between.py
+++ b/tests/test_between.py
@@ -28,7 +28,6 @@ def test_returns_true_on_valid_range(value: T, min_val: T, max_val: T):
         (None, 13, 14),
         (12, 13, 14),
         (12, None, 11),
-        (12, None, None),
         (12, 13, None),
         (12, "13.5", datetime(1970, 1, 1)),
         ("12", 20.5, "None"),
diff --git a/tests/test_length.py b/tests/test_length.py
index 65737254..c9cd1dc1 100644
--- a/tests/test_length.py
+++ b/tests/test_length.py
@@ -9,7 +9,7 @@
 
 @pytest.mark.parametrize(
     ("value", "min_val", "max_val"),
-    [("password", 2, 10), ("password", 0, 10), ("password", 8, 8)],
+    [("password", 2, None), ("password", None, None), ("password", 0, 10), ("password", 8, 8)],
 )
 def test_returns_true_on_valid_length(value: str, min_val: int, max_val: int):
     """Test returns true on valid length."""