public function getLeads($startDate, $endDate, array $params = array())
    {
        $isValidStartDate = $this->utils->isSystemDatetime($startDate);
        $isValidEndDate = $this->utils->isSystemDatetime($endDate);
        if (!$isValidEndDate || !$isValidStartDate) {
            throw new InvalidArgumentException('Invalid params: Only system date has available YYYY-MM-DDD HH:II:SS');
        }

        if ($startDate > $endDate) {
            throw new InvalidArgumentException('Invalid params: start_date > end_date');
        }

        $isOutOfLimit = $this->utils->isOutOfLimit($startDate, $endDate, LeadAcademic::LIMIT_PERIOD);
        if ($isOutOfLimit) {
            throw new InvalidArgumentException('Invalid params: Period is too large. Available only ' . LeadAcademic::LIMIT_PERIOD);
        }

        $params['date_lbound'] = $startDate;
        $params['date_ubound'] = $endDate;

        $this->normalizeParams($params);
        $response = $this->execute('/', $params);
        $data = $this->normalize($response);
        return $data['leads'];
    }