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I remember a few months ago looking at a story about humans arriving on a planet and finding a microscopic alien race. This microscopic alien race lived on a different time scale where they aged a lot faster than the humans. A short time passes for the humans and by then, the aliens are technologically advanced enough to make contact but then decide not to give any information about technologies the humans haven't discovered yet. Hopefully anybody has an idea as to who the author is and what the title is?