Currently it's technically "what's common in all 4 of those books", tho. I guess union and not intersection is a bit more suitable, but still not quite, and I'm too lazy to try to remember set theory stuff and search for something better
Currently it's technically "what's common in all 4 of those books", tho. I guess union and not intersection is a bit more suitable, but still not quite, and I'm too lazy to try to remember set theory stuff and search for something better