对…保持… keep (sth such as influence) over (sb or sth)
retain sth on〔over〕 sth
How does an aging politician retain his hold on the loyalty of the voters?
一个年迈的政客是怎样使选民继续支持他的呢?
His business has been taken over by a big corporation, but he still retains some control over it.
他的商店被一家大公司接管了,但他仍保留部分控制权。
The bank has taken further steps to retain control over the value of the pound.
这家银行已采取进一步措施来保持对英镑购买力的控制。