public function splitIsbn($isbn)
    {
        if (!$this->validateIsbn($isbn))
        {
            return false;
        } 
        $prefix         = substr($isbn, 0,3);
        $groupnumber    = $this->getGroupNumber($isbn);
        $pubnumber      = $this->getPublisherNumber($isbn);
        $prenumbers     = strlen($groupnumber)+strlen($pubnumber)+3;
        $articleNumber  = substr($isbn, $prenumbers, -1);
        $checkdigit     = substr($isbn, -1);
        return (array($prefix, $groupnumber, $pubnumber, $articleNumber, $checkdigit));        
    }