對…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?
一個年邁的政客是怎樣使選民繼續支持他的呢?
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權。
The bank has taken further steps to retain control over the value of the pound.
這家銀行已采取進一步措施來保持對英鎊購買力的控制。