Mr. Jones is a renowned international authority on the problem of overpopulation in developing countries.
琼斯先生在发展中国家人口过剩问题方面是声誉卓著的国际权威。
I bought two expensive dictionaries here half and hour ago, but I forgot to take them with me.
半小时以前我在这里买了两本很贵的辞典,但是我忘了拿走。