protected function getHighriskSpecialPrefixes() {
        if (!$this->_highriskSpecialPrefixes) {
            $this->_highriskSpecialPrefixes = new HighriskSpecialPrefixList(
                $this->version,
                $this->solution['isoCode']
            );
        }

        return $this->_highriskSpecialPrefixes;
    }