Seeking example of quality alt text in STEM book

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Colleagues,

Is anyone aware of a shining example of quality alt text on images within a STEM/science book or website?

Even more helpful would be an example of a health sciences E book with well-crafted alt text.

So far I've seen some nice examples of alt text within NASA.gov articles and separately in a CK-12 Biology I EPUB in Bookshare.

Still, examples seem to be quite limited and I'm looking for popcorn type abundance!

Ted