[c3o]

At least in the EU, whether the source is cited/linked or not doesn't make any legal difference: If there's no specific exception to copyright that allows what you're doing, you can't copy something, period. And I'm pretty sure Google's use doesn't hold up as either educational (usually doesn't cover commercial services) or as a quotation (usually requires an original work in which another is quoted for illustration/criticism/commentary).

It may be OK in the US "fair use" system, where it's up to courts to decide what's okay – I don't know the case law well enough.