BEIJING, China, Jan 13 (Reuters) - China has acquired minority stakes with special rights in two domestic units of tech giant Alibaba Group Holding Ltd (9988.HK), business registration records showed, as Beijing extends a campaign to strengthen control over online content. Beijing has been taking 'golden shares' in private online media and content companies for more than five years, and in recent years expanding such arrangements to companies with vast troves of data. The stakes taken over the last four months in the Alibaba units are the first ones to come to light for the e-commerce firm. Alibaba has been...