public function getCategoriesUsed(array $titles)
	{
		// Build the request
		$path = '?action=query&generator=categories&prop=info';

		// Append titles to the request
		$path .= '&titles=' . $this->buildParameter($titles);

		// Send the request.
		$response = $this->client->get($this->fetchUrl($path));

		return $this->validateResponse($response);
	}