后四十
Cheng and Gao edition's back forty chapters as well as its artistic value are the pending problems in "Red" study.───程高本后四十回之真伪与艺术上之得失，是红学研究的一大积案。
Forty minutes later, they were back at his place.───40分钟后，他们回到他的地方。
Bly: Donald Hall and I have been sending poems back and forth twice a week for forty years.───布莱：四十多年来，唐纳德·哈尔和我每星期都互相传送诗歌两次。
TV history, as I've said, goes back forty years.───电视的历史，正如我已经说过了，回到四十年。
back foot───后脚
back forties───四十年代后
back floats───后浮动
back copy───备份
back feet───后脚
back float───反向浮动
back foci───后焦点
back focus───[摄]后焦点；反焦点；象方焦点
back four───四卫式