public function getPreviousToken()
    {
        if (null === $this->_previousToken) {
            $tokenSelect = $this->tracker->getTokenSelect();
            $tokenSelect
                    ->andReceptionCodes()
                    ->forNextTokenId($this->_tokenId);

            if ($tokenData = $tokenSelect->fetchRow()) {
                $this->_previousToken = $this->tracker->getToken($tokenData);
                $this->_previousToken->_nextToken = $this;
            } else {
                $this->_previousToken = false;
            }
        }

        return $this->_previousToken;
    }