diff --git a/dist/files_opds-0.5.1.tar.gz b/dist/files_opds-0.5.1.tar.gz
new file mode 100644
index 0000000..b875627
Binary files /dev/null and b/dist/files_opds-0.5.1.tar.gz differ
diff --git a/files_opds/appinfo/info.xml b/files_opds/appinfo/info.xml
index f1f0524..2a590ca 100644
--- a/files_opds/appinfo/info.xml
+++ b/files_opds/appinfo/info.xml
@@ -4,7 +4,7 @@
         <name>OPDS catalog</name>
         <description>Personal OPDS catalog</description>
         <licence>AGPL</licence>
-	<version>0.5</version>
+	<version>0.5.1</version>
         <author>Frank de Lange</author>
         <requiremin>7.0</requiremin>
         <shipped>true</shipped>
diff --git a/files_opds/lib/isbn.php b/files_opds/lib/isbn.php
index b2a3e25..5499dd7 100644
--- a/files_opds/lib/isbn.php
+++ b/files_opds/lib/isbn.php
@@ -27,45 +27,55 @@ class Isbn
 
 	/**
 	 * @brief try to find a valid ISBN in the given text, using a cascade of
-	 *         regexps. Can be optimized.
+	 *         regexps. 
 	 *
 	 * @param string $text text to search through
 	 * @return string $hit ISBN on success, false otherwise
 	 */
 	public static function scan($text) {
-		if ($hits = preg_grep('/isbn/i',$text)) {
-			foreach ($hits as $hit) {
-				$hit = preg_replace('/.*ISBN(?:[ -]?1[03]:)?\s*([xX0-9-]{10,17}).*/i','$1',$hit,1);
-				//$hit = preg_replace('/isbn([ -]\(?1[03]\)?)?/i','',$hit);
-				$hit = preg_replace('/[^0-9X]/i','',$hit);
-				if(self::validate($hit)) {
-					return $hit;
+		$match = array();
+		foreach($text as $line) {
+			/* generic ISBN 10/13 pattern */
+			if(preg_match_all('/ISBN(?:[ -]?[1[03]]?)?:?\s*((97[89])?[X0-9-–]{10,14})/i',$line,$match)) {
+				foreach($match[1] as $hit) {
+					$hit = preg_replace('/[^0-9X]/i','',$hit);
+					if(self::validate($hit)) {
+						return $hit;
+					}
+				}
+			}
+
+			/* single ISBN-13 targeted pattern (canonical format) */
+			if(preg_match_all('/(97[89][ –-]?\d[ –-]?\d{4}[ –-]?\d{4}[ –-]?\d)/',$line,$match)) {
+				foreach($match[1] as $hit) {
+                                	$hit = preg_replace('/[^0-9]/','',$hit);
+                         	        if(self::validate($hit)) {
+                                	        return $hit;
+                          	      }
+				}
+                	}
+
+			/* single ISBN-13 targeted pattern (free format) */
+			if(preg_match_all('/(9[\d –-]{11,15}\d)/',$line,$match)) {
+				foreach($match[1] as $hit) {
+                                	$hit = preg_replace('/[^0-9]/','',$hit);
+                         	        if(self::validate($hit)) {
+                                	        return $hit;
+                          	      }
+				}
+			}
+        
+			/* single ISBN-10 targeted pattern */
+			if(preg_match_all('/(\d[\d –-]{8,11}[\dX])/i',$line,$match)) {
+				foreach($match[1] as $hit) {
+					$hit = preg_replace('/[^0-9X]/i','',$hit);
+					if(self::validate($hit)) {
+						return $hit;
+					}
 				}
 			}
 		}
 
-		/* single ISBN-13 targeted pattern */
-		if ($hits = preg_grep('/\d{3}[ -]?\d[ -]?\d{4}[ -]?\d{4}[ -]?\d/', $text)) {
-			foreach ($hits as $hit) {
-				$hit = preg_replace('/.*(\d{3}[ -]?\d[ -]?\d{4}[ -]?\d{4}[ -]?\d).*/','$1',$hit,1);
-				$hit = preg_replace('/[^0-9]/i','',$hit);
-				if(self::validate($hit)) {
-					return $hit;
-				}
-			}
-		}
-
-		/* single ISBN-10 targeted pattern */
-		if ($hits = preg_grep('/\d[\d -]{8,11}[\dX]/i', $text)) {
-			foreach ($hits as $hit) {
-				$hit = preg_replace('/.*(\d[\d -]{8,11}[\dX]).*/','$1',$hit,1);
-				$hit = preg_replace('/[^0-9X]/i','',$hit);
-				if(self::validate($hit)) {
-					return $hit;
-				}
-			}
-		}
-	
 		return false;
 	}
 
@@ -115,22 +125,28 @@ class Isbn
 	 * @return bool true if valid ISBN-10
 	 */
         static function isIsbn10 ($isbn) {
-                $checksum = 0;
-                for ($i = 0; $i < 10; ++$i) {
-                        if (!isset($isbn{$i})) {
-                                return false;
-                        }
-                        if ('X' === $isbn{$i}) {
-                                $digit = 10;
-                        } elseif (ctype_digit($isbn{$i})) {
-                                $digit = $isbn{$i};
-                        } else {
-                                return false;
-                        }
-                        $checksum += $digit * intval(10 - $i);
-                }
+		$len = strlen($isbn);
+		if ($len == 10) {
+			//Calculate check digit
+			$check = 0;
+			for ($i = 0; $i < 9; $i++) {
+				if ($isbn[$i] === "X") {
+					$check += 10 * intval(10 - $i);
+				} else {
+					$check += intval($isbn[$i]) * intval(10 - $i);
+				}
+			}
+			$check = 11 - $check % 11;
+			if ($check === 10) {
+				$check = 'X';
+			} elseif ($check === 11) {
+				$check = 0;
+			}
 
-                return 0 === $checkSum % 11 ? true : false;
+			return ($check == $isbn{$len - 1});
+		}
+
+		return false;
         }
 
 	/**
@@ -139,15 +155,25 @@ class Isbn
 	 * @return bool true if valid ISBN-13
 	 */
         static function isIsbn13 ($isbn) {
-                $checksum = 0;
-                for ($i = 0; $i < 13; $i +=2) {
-                        $checksum += $isbn{$i};
-                }
-                for ($i = 1; $i < 12; $i +=2) {
-                        $checksum += $isbn{$i} * 3;
-                }
+		$len = strlen($isbn);
+		if ($len == 13) {
+			//Calculate check digit
+			$check = 0;
+			for ($i = 0; $i < 12; $i += 2) {
+				$check += substr($isbn, $i, 1);
+			}
+			for ($i = 1; $i < 12; $i += 2) {
+				$check += 3 * substr($isbn, $i, 1);
+			}
+			$check = 10 - $check % 10;
+			if ($check === 10) {
+				$check = 0;
+			}
 
-                return 0 === $checkSum % 10 ? true : false;
+			return ($check == $isbn{$len - 1});
+		}
+
+		return false;
         }
 }
 
diff --git a/files_opds/lib/meta.php b/files_opds/lib/meta.php
index 1ebdca8..c0f87f8 100644
--- a/files_opds/lib/meta.php
+++ b/files_opds/lib/meta.php
@@ -119,7 +119,7 @@ class Meta
          * @return array of metadata
          */
         public static function get($id) {
-		if (!($meta = self::load($id)) || (isset($meta['rescan']) && time() > $meta['rescan'])) {
+		if (!($meta = self::load($id)) || (isset($meta['rescan']) && time() > strtotime($meta['rescan']))) {
 			if(isset($meta['rescan'])) {
 				$meta['rescan'] = null;
 			}