知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。Early 70s scifi novel about underground people, caste is decided by the color of one's poncho, and everyone eats mouldy grainThe generic time period is “marketing resources” or (somewhat obnoxiously) “promos.” That’s the phrase utilised wi