[EnglishTeacher79]

I've been trying to find some information regarding plural superlatives or whatever this is called. By this I mean the grammar used in the following sentence: "The three most important things are..." Normally, we're taught the the superlative is for one thing, but of course we also use sentences like "the three most important things" and "the second most important thing", etc. I'm trying to find out information about this use of the superlative to teach my students. Anyone could refer me to any place in books or the web where I can find more information about this? Thanks.