diff --git a/src/helpers/citation.js b/src/helpers/citation.js
index a419441..3b31ca4 100644
--- a/src/helpers/citation.js
+++ b/src/helpers/citation.js
@@ -40,6 +40,7 @@ export function inline_cite_long(keys){
 }
 
 function author_string(ent, template, sep, finalSep){
+  if (ent.author == null) { return ''; }
   var names = ent.author.split(' and ');
   let name_strings = names.map(name => {
     name = name.trim();
diff --git a/src/transforms/citation.js b/src/transforms/citation.js
index cde18ca..b45d47b 100644
--- a/src/transforms/citation.js
+++ b/src/transforms/citation.js
@@ -95,6 +95,7 @@ export default function(dom, data) {
   }
 
   function author_string(ent, template, sep, finalSep){
+    if (ent.author == null) { return ''; }
     var names = ent.author.split(' and ');
     let name_strings = names.map(name => {
       name = name.trim();