diff --git a/oai2exception.php b/oai2exception.php
index f2d6635..84a095c 100644
--- a/oai2exception.php
+++ b/oai2exception.php
@@ -1,24 +1,42 @@
 <?php
+/**
+ * Simple OAI-PMH 2.0 Data Provider
+ * Copyright (C) 2011 Jianfeng Li
+ * Copyright (C) 2013 Daniel Neis Araujo <danielneis@gmail.com>
+ * Copyright (C) 2017 Sebastian Meyer <sebastian.meyer@opencultureconsulting.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
 
 class OAI2Exception extends Exception {
 
-    function __construct($code) {
-
+    public function __construct($code) {
         $this->errorTable = array(
             'badArgument' => array(
-                'text' => "The request includes illegal arguments, is missing required arguments, includes a repeated argument, or values for arguments have an illegal syntax.",
+                'text' => 'The request includes illegal arguments, is missing required arguments, includes a repeated argument, or values for arguments have an illegal syntax.',
             ),
             'badResumptionToken' => array(
-                'text' => "The value of the resumptionToken argument is invalid or expired",
+                'text' => 'The value of the resumptionToken argument is invalid or expired.',
             ),
             'badVerb' => array(
-                'text' => "Value of the verb argument is not a legal OAI-PMH verb, the verb argument is missing, or the verb argument is repeated.",
+                'text' => 'Value of the verb argument is not a legal OAI-PMH verb, the verb argument is missing, or the verb argument is repeated.',
             ),
             'cannotDisseminateFormat' => array(
-                'text' => "The metadata format identified by the value given for the metadataPrefix argument is not supported by the item or by the repository.",
+                'text' => 'The metadata format identified by the value given for the metadataPrefix argument is not supported by the item or by the repository.',
             ),
             'idDoesNotExist' => array(
-                'text' => "The value of the identifier argument is unknown or illegal in this repository.",
+                'text' => 'The value of the identifier argument is unknown or illegal in this repository.',
             ),
             'noRecordsMatch' => array(
                 'text' => 'The combination of the values of the from, until, set and metadataPrefix arguments results in an empty list.',
@@ -37,4 +55,5 @@ class OAI2Exception extends Exception {
     public function getOAI2Code() {
         return $this->code;
     }
+
 }