《新唐书·列传·卷一百四十四》
子孙死，父母早晚都哭悼；父母死，子孙不哭，也没有服丧期。
子孙死，父母旦夕哭；父母死则否，亦无丧期。
When their children died, parents would mourn and cry morning and evening. When parents died, their descendants did not cry and there was no mourning;