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To address this issue, a framework is suggested that defines material response coefficients extractable from measured spectra in terms of averages of microscopic quantities that characterize an interface. Such response coefficients can be theoretically calculated for comparison with the extracted ones. Comments on works in three areas that have garnered considerable attention in recent years are given. It is seen that these results are either incorrectly presented, misinterpreted, or overstated.<\/jats:p>","DOI":"10.1063\/5.0304596","type":"journal-article","created":{"date-parts":[[2025,12,30]],"date-time":"2025-12-30T12:49:17Z","timestamp":1767098957000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":5,"title":["Perspectives on surface sum-frequency spectroscopy"],"prefix":"10.1063","volume":"163","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5075-5255","authenticated-orcid":false,"given":"Y. 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