diff --git a/lagebild/lagebild.js b/lagebild/lagebild.js
index baf64ad..8ee6148 100644
--- a/lagebild/lagebild.js
+++ b/lagebild/lagebild.js
@@ -476,10 +476,10 @@ var Lagebild = {
         var srcMap = {};
         var sources = v.sources_json || [];
         for (var i = 0; i < sources.length; i++) {
-            srcMap[sources[i].nr] = sources[i];
+            srcMap[String(sources[i].nr)] = sources[i];
         }
         var self = this;
-        html = html.replace(/\[(\d+)\]/g, function(match, nr) {
+        html = html.replace(/\[(\d+[a-z]?)\]/g, function(match, nr) {
             var src = srcMap[nr];
             if (src && src.url) {
                 return '<a class="citation-ref" href="' + self.esc(src.url) + '" target="_blank" rel="noopener" title="' + self.esc(src.name || '') + '">[' + nr + ']</a>';