diff --git a/vendor/renanbr/bibtex-parser/src/Parser.php b/vendor/renanbr/bibtex-parser/src/Parser.php
index 1c0cfa0..1f83785 100644
--- a/vendor/renanbr/bibtex-parser/src/Parser.php
+++ b/vendor/renanbr/bibtex-parser/src/Parser.php
@@ -266,7 +266,7 @@ class Parser
      */
     private function readTagName($char)
     {
-        if (preg_match('/^[a-zA-Z0-9_\+:\-\.\/\x{00C0}-\x{01FF}]$/u', $char)) {
+        if (preg_match('/^[a-zA-Z0-9_\&\+:\-\.\/\x{00C0}-\x{01FF}]$/u', $char)) {
             $this->appendToBuffer($char);
         } elseif ($this->isWhitespace($char) && empty($this->buffer)) {
             // Skips because we didn't start reading