diff --git a/prune-orphans.sh b/prune-orphans.sh
index cad84be..b5562fa 100755
--- a/prune-orphans.sh
+++ b/prune-orphans.sh
@@ -1,20 +1,24 @@
 #!/usr/bin/env bash
-# Remove content/zettels/*.md whose org source in ~/Cloud/brain no longer exists.
+# Remove content/<section>/*.md (zettels and bibliography) whose org source in ~/Cloud/brain no longer exists.
 # Dry run by default; pass --delete to actually remove files.
 set -euo pipefail
 
 brain=~/Cloud/brain
-zet="$(cd "$(dirname "$0")" && pwd)/content/zettels"
+content="$(cd "$(dirname "$0")" && pwd)/content"
+sections=(zettels book phdthesis inbook techreport article inproceedings websites)
 
 count=0
-for md in "$zet"/*.md; do
-  name=$(basename "$md" .md)
-  [[ $name == _index ]] && continue
-  if [[ ! -f "$brain/$name.org" ]]; then
-    echo "orphan: $md"
-    [[ ${1:-} == --delete ]] && rm "$md"
-    count=$((count + 1))
-  fi
+for section in "${sections[@]}"; do
+  for md in "$content/$section"/*.md; do
+    [[ -e $md ]] || continue
+    name=$(basename "$md" .md)
+    [[ $name == _index ]] && continue
+    if [[ ! -f "$brain/$name.org" ]]; then
+      echo "orphan: $md"
+      [[ ${1:-} == --delete ]] && rm "$md"
+      count=$((count + 1))
+    fi
+  done
 done
 
 if [[ $count -eq 0 ]]; then