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I think it would make the most sense to use the primary language in quotations, because as the previous answer stated, using too many italics would end up making the literature seem cluttered.
Answer
#3: Attribution notice added
Source: https://writers.stackexchange.com/a/19601 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/