diff --git a/omicron/ssg/output/content.py b/omicron/ssg/output/content.py
index 2b8a90c..470deb5 100644
--- a/omicron/ssg/output/content.py
+++ b/omicron/ssg/output/content.py
@@ -1,6 +1,6 @@
 import re
 from typing import TYPE_CHECKING
-from omicron.ssg.output.output import Output, OutputError
+from omicron.ssg.output.output import Output, OutputError, is_normalized
 from pathlib import Path
 from datetime import date
 
@@ -31,6 +31,10 @@ class Content(Output):
         super().__init__(site, Content.build_path(section, slug))
         if tags is None:
             tags = set()
+        if not source.is_absolute():
+            raise ContentError("content source path must be absolute")
+        if not is_normalized(source):
+            raise ContentError("content source path must be normalized")
         self.source = source
         self.section: str = section
         self.created = created
diff --git a/omicron/ssg/site.py b/omicron/ssg/site.py
index 387fe36..3360ba0 100644
--- a/omicron/ssg/site.py
+++ b/omicron/ssg/site.py
@@ -38,6 +38,7 @@ class Site:
         self.other_outputs: list[Output] = []
         self.by_tag: dict[str, list[Content]] = {}
         self.by_path: dict[Path, Output] = {}
+        self.by_source: dict[Path, Content] = {}
         self.by_section: dict[str, list[Content]] = {}
         self.tags_by_count: list[tuple[str, int]] = []
 
@@ -123,6 +124,10 @@ class Site:
             self.by_path[d.destination] = d
             self.directories.append(d)
 
+    def add_by_source(self, content: Content) -> None:
+        assert content.source.is_absolute(), "Expecting content to have absolute source"
+        self.by_source[content.source] = content
+
     def home_url(self) -> str:
         return self.base_dir.as_posix()
 
@@ -172,6 +177,7 @@ class Site:
                 self.add_by_path(content)
                 self.add_by_section(content)
                 self.add_by_tag(content)
+                self.add_by_source(content)
                 self.content.append(content)
         self.update_tags_by_count()
         for index in discover_index(self):