diff --git a/ogc/bblocks/oas30.py b/ogc/bblocks/oas30.py
index 2d16e8e..191eb09 100644
--- a/ogc/bblocks/oas30.py
+++ b/ogc/bblocks/oas30.py
@@ -1,7 +1,9 @@
 #!/usr/bin/env python3
 from __future__ import annotations
 
+import argparse
 import logging
+import os
 import re
 from builtins import isinstance
 from collections import deque
@@ -10,7 +12,7 @@
 from urllib.parse import urlparse
 
 from jsonpointer import resolve_pointer
-from ogc.na.util import is_url, load_yaml
+from ogc.na.util import is_url, load_yaml, dump_yaml
 
 from ogc.bblocks.util import load_file_cached, PathOrUrl
 
@@ -302,9 +304,15 @@ def schema_to_oas30(schema_fn: Path, schema_url: str, bbr: BuildingBlockRegister
     }
 
 
-def oas31_to_oas30(document: dict, document_location: PathOrUrl | str, bbr: BuildingBlockRegister | None,
+def oas31_to_oas30(document: dict, document_location: PathOrUrl | str, bbr: BuildingBlockRegister | None = None,
                    x_defs_path='/x-defs', target_version='3.0.3'):
 
+    if not isinstance(document, dict):
+        if isinstance(document, Path) or not is_url(document):
+            document = load_yaml(filename=document)
+        else:
+            document = load_yaml(url=document)
+
     # == 1. Bundle
     if x_defs_path[0] != '/':
         x_defs_path = '/' + x_defs_path
@@ -430,6 +438,12 @@ def fn(subschema: dict[str, Any], parent_is_properties=False, property=None, **k
     def process_path_item_object(o: dict):
         if not o:
             return
+
+        ref = o.get('$ref')
+        if ref:
+            process_path_item_object(resolve_pointer(root_schema, ref[1:]))
+            return
+
         for op_key in OAS_OPERATION_KEYS:
             operation = o.get(op_key)
             if operation:
@@ -442,17 +456,39 @@ def process_path_item_object(o: dict):
     def process_operation_object(o: dict):
         if not o:
             return
-        for parameter in o.get('parameters', []):
-            resolve_parameter(parameter)
-            process_schema_object(parameter)
-            process_content_object(parameter)
+
+        ref = o.get('$ref')
+        if ref:
+            process_operation_object(resolve_pointer(root_schema, ref[1:]))
+            return
+
+        parameters = o.get('parameters')
+        if isinstance(parameters, dict):  # $ref!
+            parameters = resolve_pointer(root_schema, parameters['$ref'][1:])
+        if parameters:
+            for parameter in parameters:
+                resolve_parameter(parameter)
+                process_schema_object(parameter)
+                process_content_object(parameter)
 
         process_content_object(o.get('requestBody'))
 
-        for response in o.get('responses', {}).values():
-            process_content_object(response)
-            for header in response.get('headers', {}).values():
-                process_schema_object(header)
+        responses = o.get('responses')
+        if responses:
+            ref = responses.get('$ref')
+            if ref:
+                responses = resolve_pointer(root_schema, ref[1:])
+            if responses:
+                for response in o.get('responses', {}).values():
+                    process_content_object(response)
+                    headers = response.get('headers')
+                    if headers:
+                        ref = responses.get('$ref')
+                        if ref:
+                            headers = resolve_pointer(root_schema, ref[1:])
+                    if headers:
+                        for header in headers.values():
+                            process_schema_object(header)
 
         for callback in o.get('callbacks', {}).values():
             process_operation_object(callback)
@@ -460,7 +496,18 @@ def process_operation_object(o: dict):
     def process_content_object(o: dict):
         if not o:
             return
+
+        ref = o.get('$ref')
+        if ref:
+            process_content_object(resolve_pointer(root_schema, ref[1:]))
+            return
+
         content = o.get('content')
+        if content:
+            ref = content.get('$ref')
+            if ref:
+                content = resolve_pointer(root_schema, ref[1:])
+
         if content:
             for schema_object in content.values():
                 # remove description because 3.0 doesn't support it
@@ -515,3 +562,40 @@ def process_document():
     root_schema['openapi'] = target_version
 
     return root_schema
+
+
+def _main():
+    parser = argparse.ArgumentParser(
+        description='Downcompiles OpenApi 3.1 documents to 3.0',
+    )
+
+    parser.add_argument(
+        'document',
+        help='Document to downcompile',
+    )
+
+    parser.add_argument(
+        '--url',
+        help='Canonical URL of document',
+    )
+
+    parser.add_argument(
+        '-o',
+        '--output',
+        help='Output file'
+    )
+
+    args = parser.parse_args()
+
+    document_location = PathOrUrl(args.url or args.document)
+
+    result = oas31_to_oas30(args.document, document_location)
+
+    if not args.output:
+        print(dump_yaml(result))
+    else:
+        dump_yaml(result, args.output)
+
+
+if __name__ == '__main__':
+    _main()