author A writes on
Topic B and in this context uses
quotation C which is not from the same field and appears highly original in
Topic B. I then read this article, and I am myself writing on
Topic B. I find the quote so useful or relevant, that I quote it myself.
Am I obliged to mention where I found the quote (namely in
author A)? Or can I just use the quote? Where are the boundaries here, what do you think is acceptable, what is not? Also, if it is not ethical, that's one thing - but is it also plagiarism?
PS: If anyone has a good title for this sort of question, please feel free to edit. Not sure how to name this.