diff --git a/etc/sources.scm b/etc/sources.scm
index 71d157d..515cf00 100644
--- a/etc/sources.scm
+++ b/etc/sources.scm
@@ -1,5 +1,5 @@
 ;;; Preservation of Guix
-;;; Copyright © 2022 Timothy Sample <samplet@ngyro.com>
+;;; Copyright © 2022, 2024 Timothy Sample <samplet@ngyro.com>
 ;;;
 ;;; This file is part of Preservation of Guix.
 ;;;
@@ -61,6 +61,7 @@ FROM fods f
 WHERE f.algorithm = 'sha256'
     AND (fr.reference LIKE '\"%'
         OR fr.reference LIKE '(\"%')
+    AND fr.reference LIKE '%bioconductor.org%'
     AND NOT fr.is_error
     AND f.is_in_swh IS NOT NULL
     AND NOT f.is_in_swh")
@@ -85,22 +86,25 @@ Subresource Integrity metadata value."
   (define b64 (base64-encode bv))
   (string-append "sha256-" b64))
 
-(define (web-reference-urls reference)
+(define (web-reference-filename reference)
   (define uris
     (match (call-with-input-string reference read)
       ((urls ...) (map string->uri urls))
       (url (list (string->uri url)))))
-  (append-map (lambda (uri)
-                (map uri->string
-                     (maybe-expand-mirrors uri %mirrors)))
-              uris))
+  (or (any (lambda (uri)
+             (and (string-suffix? "bioconductor.org" (uri-host uri))
+                  (basename (uri-path uri))))
+           uris)
+      (error "Not a 'bioconductor.org' refernce" reference)))
 
 (define (record->url-source rec)
   (match-let ((#(digest reference) rec))
-    (let ((urls (web-reference-urls reference))
-          (integrity (nix-base32-sha256->subresource-integrity digest)))
+    (let* ((filename (web-reference-filename reference))
+           (url (string-append "https://bordeaux.guix.gnu.org/file/"
+                               filename "/sha256/" digest))
+           (integrity (nix-base32-sha256->subresource-integrity digest)))
       `(("type" . "url")
-        ("urls" . ,(list->vector urls))
+        ("urls" . ,(vector url))
         ("integrity" . ,integrity)))))
 
 (define (lookup-missing-sources db)