Beijing has extended an olive branch to French cognac producers by promising a “significant” tax refund if they cooperate with its anti-dumping investigation into European Union brandy sold in China, according to an industry source with knowledge of the matter.Major brands Hennessy, Martell and Rémy Martin have been offered the terms, said the person, who spoke anonymously due to the sensitivity of the issue.To qualify, producers must agree to Beijing’s demands, commit to a minimum selling...