body: I quoted extensively from Quirk et al's book on English grammar in [one of my recent answers](https://ell.stackexchange.com/a/80432/2127) on ELL StackExchange, and a thought came to me: what is the maximum amount beyond which a quotation might infringe upon the copyright? 
  
  
  I don't want for my answers to be lost because someday some copyright holder would deem them infringing. 
  
  
  And what if, say, Quirk et al.'s book will be quoted in minute excerpts across thousands of answers, but in aggregate these will constitute a sizable share of the book? Would that be an infringement?
  
  
  I first [asked this question](https://ell.meta.stackexchange.com/questions/2910/copyright-issues-with-grammar-literature-quotations) on ELL SE meta, but was advised to migrate it here.
  
  
  
  
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  P.S. To clarify: Quirk et al.'s "[A Comprehensive Grammar of the English Language](https://en.wikipedia.org/wiki/A_Comprehensive_Grammar_of_the_English_Language)" is part of the Holy Scripture for English grammarians. (0: Because of that, it's very likely to be quoted in answers on English Language Learners Stack Exchange. 
  
  
  
title: Copyright issues with grammar literature quotations on ELL StackExchange